I have used coupons at Arby's and other fast food restaurants and have never had this h...

I have used coupons at Arby's and other fast food restaurants and have never had this happen. I used the $* roast beef combo coupon. I was told my total was $*.**. I said that cannot be correct, there is no way the sales tax is over $* on a $* item. The cashier told me yes it is, it charges you double tax. It charges you the tax on the original priced item and then an additional tax on the total. I completely understand it you want to charge me the pre coupon tax amount (I don't agree with it not have I every known it to happen, but I can at least understand). What I don't understand is why I was charged $.** of tax and then an additional $.** tax on my sub total. I visit Arby's frequently but after yesterday I will be looking for other places to eat.