Apple - Why doesn't OS X require graphics card driver updates?
Apple makes its own drivers & they are included in the OS updates.
The way to be up to date on drivers is to always be running the latest OS.
There is debate over whether Apple make the entire driver set themselves, or just take NVidia/AMD's core code & add their own hardware/OS-specific code to it. The latter seems more plausible to me, but either is just speculation.
The end result, though, is that there are rarely issues with Apple graphics drivers & regular software or games; again speculation, but for games I imagine they write to a pre-defined rule-set, rather than try to constantly be pushing the boundaries.
As noted elsewhere, NVidia themselves make OS X drivers for Quadro cards but these are aftermarket cards anyway, not supplied in any Mac build option available directly from Apple.
Apple provides core drivers, currently up to OpenGL 4.1 or 3.3 - depending on your card, of course - plus legacy drivers for OGL 2.1 compatibility. Which one you get to use in any particular game etc is up to the writers of that game.
Traditionally, if your card has full OpenGL support for the first monitor, it will also have it on the second, unlike many PC cards with 'clipped' performance on the 2nd monitor.
Link to OpenGL support by Mac model
After comments & other answers here…
NVidia do have their own release for certain Mac GPUs - this is the current driver as of December 2015
However, they are predominantly for the Quadro series of aftermarket cards rather than default cards supplied by Apple.
There is also support for some cards which have been legacied by Apple - namely the GeForce 680, 285, 120 & 8800
There is mention of beta support for some recent mobile cards, presumably as Apple are dropping legacy support on these in favour of AMD in the current lineup.
To hazard an educated guess, I would say that driver updates are most likely rolled into Mac OS X version upgrades and point updates. If you're concerned about the updates available for your particular card, (especially if it is not original to the Mac you're using,) it behooves you to visit the manufacturer's respective web sites to check. You mentioned NVIDIA: here's the link to the drivers available for download. Looks like plenty of options for many operating systems. (Mac OS X NVIDIA drivers are only available for Quadro-series boards, tho'.)
Besides the drivers that Apple bundles with OS X updates, Nvidia also provides their own driver updates for their GeForce cards — yes, even the "mobile" cards that Apple puts in Macs. As far as I know, this is not true of AMD and Intel. In the case of your Retina MacBook Pro with an Nvidia card, there's beta support with Nvidia's latest drivers.
Nvidia's graphics drivers for OS X can be downloaded straight from their website, and as such they're sometimes called Nvidia Web Drivers. They're somewhat hard to find if you just go through Nvidia's driver search feature, but they're an easy find if you just Google "Nvidia driver OS X" + your OS X version (e.g. 10.11.2).
For example, here is Nvidia's current (as of December 2015) driver for OS X El Capitan 10.11.2. As it says in the release notes, support for some newer models of iMacs and MacBook Pros with GeForce cards is in beta.
Note that I don't recommend installing Nvidia's drivers (especially beta ones) unless you know what you're doing, and you have a good reason to switch from the default (Apple-provided) ones that come with OS X. The default drivers are probably more thoroughly tested and stable, less likely to break your Mac, and are supported officially by Apple. If you do install the Nvidia driver, though, you'll always have the option to switch back to the default driver or even uninstall the Nvidia driver via System Preferences. You'll also be able to update the driver from there.
A good reason to try out Nvidia's driver might be if you use your Mac for gaming, or you run any other apps that use OpenGL. On my MacBook Pro with OS X 10.11.2 and an Nvidia GT 650m card, Cinebench's OpenGL test gives a very slight edge to Nvidia's drivers (~52 fps) vs. Apple's (~49 fps).