There are legitimate arguments for both sides. I don't blame CVS because it's probably corporate policy to sell things for x and expect x payment for it. Corporations do not operate as humanistic entities.
Having said that, if the clerk, a bystander, or someone else couldn't help out to the tune of a buck or let something slide then that's a real bummer.
Conversely, I've also been heckled by people at gas stations who claim they didn't have enough gas and are in dire straits if they can't get a few bucks of your gas. They'll even promise to pay you, a complete stranger, back.
This is not a case of right or wrong. It's a strict judgment call.