OK, here's a trick that they wont tell you at the GG.

If you have doubles or triples & the item is on sale the coupon will double or triple to the retail price. For example, if you are buying something that is normally 1.99 and it is 1.00 on sale. You have a 75/1 coupon and you are doubling 1.00 sale price - 75x2 = (.50). Triples would be 1.99 - 75x3 up to 1.99 = zero. If I am buying something that does this, especially in multiples, then I grab a gift card to absorb the overage. Yes, if you had grabbed a $10 GC you would have paid an extra $7 BUT you would have gained that $3 and just use the GC on your next trip. You aren't out any money.

If it is a small balance just grab a candy bar or two or a magazine to cover the overage.