Open a Target credit account and SAVE!! (a penny???)

I was in Target today, checking out their outdoor stuff when my daughter grabbed me by the hand, told me to close my eyes, and proceeded to guide me to one of those humungeous offset umbrellas (I'm having my backyard landscaped and have been thinking about buying one). I opened my eyes and gasped. I mean this thing was huge, and it was a beautiful cranberry red.
I checked out the price and did a double-take. If you've done any shopping at Target, just about every time you go through the check-out stand, they ask if you want to save 10% by opening a credit card account. Well, I think someone was asleep when they created this item tag, 'cause all I would save is one whole penny. Whoopee. I couldn't help but wonder how in the world a math error of this type could even happen in the first place. I would think they have a standard program that automatically figures 10% off of the list price, which in this case would mean a reduction of $39.99. Oh, well. I guess I may never know.