Prevent Mobile Safari from presenting toolbar when bottom of viewport is tapped

No there is not. You can control the content of your webpage but not the behavior of the safari app.

The simple solution here is to add about 50px padding-bottom on your bottom most div. Safari seems to think that you are trying to access the bottom navigation bar, unless you click well above the bottom area. With extra padding at bottom, the user will click much higher on the page (not always, but in general).