(A customer is trying to combine coupons on one purchase; this is not allowed. One is a coupon that allows her to buy expensive candles for half off and the other is a basic “free item with any purchase” coupon.)

Me: “Oh, sorry ma’am, we’ll have to do this as two separate purchases. We’ll use your candle coupon first, then, if you just add another item you’ll qualify to use your second coupon and get your free item.”

Customer: “But I was purchasing the candle to get the free item.”

Me: “Yes, but you can’t use the coupon on the candle and then use a second coupon on the same purchase. But it’s okay, you can buy one of these cheap $1.00 items to qualify for the second coupon, I’ll just ring these items up separately.”

Customer: “Or maybe I don’t buy anything at all!”

(The customer swipes her cheap mailer coupon off the counter and walks away, leaving me holding her exclusive candle coupon.)