Just a suggestion for those of you having trouble... A $50 bill does not equal two $25 bills. You have to think of each bill as a whole unit because you have an empty cash register, and can't make change until you're given it.

I think that your problem probably stems from the fact that you can also give change for a $100 bill in the form of one $50 bill and one $25 bill (instead of three $25 bills).