Toys R Us had Harry Potter on the special pre-order program. Pre-order for $5, get the DVD for a balance of 7.99. That part's great. But when I went to pick it up, I was a little surprised that I paid a total of 9.37. The tax was $1.38. The short answer is that the tax was on the total amount. I didn't stop to do the math...
The "total amount" they taxed was the price before any discount. Toys R Us' pre-order program gives a discount for pre-order, and they don't calculate the reduced price and then tax that. They tax the before-discount price. It's as if I'd paid $5 to buy a $15-off coupon. So the sales tax was on $22.99.
The worst part is the friendly "YOU SAVED $15.00" at the bottom of the receipt. Uh, no, I saved $10. I PRE-PAID the $5.00.
Inaccuracy in communications annoys me.