dear valued customer:
yes, very often we have coupons (especially valuable during our "best sale of the decade days"). you will receive these coupons in a mailing with your monthly statement or by clipping them from the newspaper. the proper protocol for use of said coupons is as follows:
you (henceforth known as the customer) will approach my counter with your deck of coupons clutched in one hand and your clothing selections in the other. you will then fan your coupons as if playing a card game. you will say to me, "will the 20% coupon work on this purchase." in turn, i will scan the price tag on the item and either reply, "yes, i can use that coupon" or "no, i cannot. go fish."
in a more complicated game, we can fan out all coupons on my counter (henceforth known as "showing your hand" so that i can chose the best combination of coupons in order to save you the most money. for example, if you have a $10 off on a $30 purchase coupon AND a 20% off coupon, i could suggest that we ring up your purchase in two separate transactions.
if i am in a bad mood, or if you have up to this point been a disagreeable customer, or if the use of coupons game threatens to cut into my daily sales goal, i may or may not play along.