PornoDoggy...my husband's view on ethics is "hey, ya tried to do the right thing and the bitch wouldn't let you."
(I got sidetracked into "I so HATE the way people treat children!!" so at the moment I'm not in a good place to say what I would have done. No. Wait. I remember myself at 14. I would have cried. Then I would have gone home and told my parents...who would have had the cashier gutted and returned the money for me.)
I once had a quarter forced on me by a neighbor because I helped her carry in her groceries. I must have been ten or eleven. My mother made me go give it back, saying "you don't take money for doing what you're supposed to do."
Many, many years later, the experience was repaid when a little neighbor boy helped the adult me carry in my groceries. I was half through the sentence of offering him something when he did the "hands behind the back, smile, shake the head, smile, throw it in reverse" thing I learned to do.
Cool, and here's to you, Mom.