T-SQL to trim a datetime to the nearest date?

One way is to change getdate() to your column name,

select dateadd(dd, datediff(dd, 0, getdate())+0, 0)

Why not convert straight to date:

select convert(date, getdate())

This truncates days, not rounds. To round Days do this:

select convert(date, getdate() + 0.5)