Sorry to be harsh, but as an experienced coupon user that sort of attitude bugs the snot out of me. Coupons are a good way to bring down a grocery bill, and they're necessity for a lot of people. I've never hit one of those 90% off grocery shopping trips, but I've done 100% off at CVS before now. If the person had all legitimate coupons that weren't expired (and probably had those idiotic brain-damaged new bar codes that no one can scan) then the OP should have watched and learned.

I have left my order on the belt and walked before, but only when a manager all but accused me of using fake coupons. Internet printables weren't in wide use yet, but not posting a policy change and then all but calling someone a liar and thief when she followed the old one isn't the best way to attract repeat business. He didn't last long; the chain canned him.