It Must Be Free!!

A word of advice from a person who has worked in retail:

When the item you're purchasing does not immediately scan, telling the cashier, "It must be free!" is not funny. As a matter of fact, the cashier has probably heard that little joke 3 times that day already. On average, the cashier has likely heard your joke over a dozen times in the past week alone. After hearing said joke over 600 times per year, it really loses it's punch.

So the next time you're buying something and it doesn't scan correctly at first. Just keep your fool mouth shut. You'll have made the attendant very happy.