Just as anywhere else, it's always safe not to lie (but I think if you're off by a couple hours, it's not a big deal).
Are you talking about the rotation or nonrotation hours? For my nonrotation hours I just estimate how many hours I do, the preceptor signs off, and that's that. I don't think anyone from the board has ever checked my hours, but they always could if they wanted to. It's better to just be truthful and to be safe.
But I heard that on rotations if the preceptor signs off early, that's OK, just go home.