Here's what I bought: three boxes of Vanilla Yogurt Cheerios, a bag of rolls, a pack of cheese singles, and a big pitcher of Sunny D. I left the store with all of that plus an extra $1.93 in cash.

The secret is knowing that some coupons are stackable, meaning you can use multiple coupons on one item. Generally, you can only combine a manufacturer's coupon and a store-specific coupon. There's a real science to all of this, because the rules of coupon usage are dependent upon two often-opposing forces: the computer-controlled cash register system and the ability and focus of the clerk himself. Either half can reward you or screw you, however the situation rolls out. Today I had a doozy.

Follow along... the three boxes of cereal were already on a store discount (with my valued shopper card). So there's $1.50 right off the top. Then you see the rolls, cheese and drink... with only a nine cent store discount to show for it.

This operation started at the You Scan It section, so I was ostensibly in charge of all the couponing. Although the receipt re-organized it, the first coupon I scanned was the $10 store rewards offer. This one came first because I wasn't really doing any math on this, and I wanted to be sure the $10 was usable before I got to all the other coupons I had on hand. Ten bucks saved, no problem.

Then I went into my Yogurt Cheerios coupons, some being manufacturer and some from the store itself. In fact, I found an additional $1.50 coupon in the cereal aisle on that very lunch trip. The You Scan didn't like my first coupon, so I had to present that to the one human in charge of the self-serve zone. She had to force it through, and then asked me if I had any other coupons, so she could handle them all for me. I gave her every one I had, and she forced them all through. The machine even doubled my 75 cent coupon!

Total Before Savings: $17.10. Total Savings: $19.09. So I ended up owing the store negative $1.99... or rather, they owed me $1.99.

Hilariously, the system somehow charged tax on my negative $1.99... ah well, let the state have their six cents.

End result: a pair of confused cashiers handed me one dollar and ninety-three cents in change. Hey, it's what the computer told them to do. My guess is that they shouldn't have forced through quite so many coupons, although they were all legitimately for the amount and type of Cheerios I purchased. You'd think that, when presented with a negative total, they'd pause the system and make me take back a coupon or two. At no time did I raise a fuss; I rather enjoyed spectating the entire thing. At one point I even asked if it would be easier if I added something to the order so that the total would go positive again.

Oh no, thank you.