Weird, I've never seen this rule enforced in stores, only in public transportation. In fact, I eat at an all you can eat pizza place every Thursday afternoon that charges me $15.30, I always pay with a $20 bill and get a $5 one back.  I'm all for bullying fatties because it hastens their inevitable heart attack, but I don't see why any store would hold 6 cents against a thin costumer that's already spending 15 bucks in overpriced ice cream.