"If you are in a 5 max game in late position or the button with a hand like 55 or 77 and everyone folds to you, what is your play? "


Raise, without a doubt.


"What if your bet is called on the flop? Keep bluffing or give up? "


That depends entirely on the texture of the board.

If you have problems with playing these hands (especially postflop) it might be advisable to post some, with all the information you had about the situation at that time.


Regards