The item itself is 72.99 and the store is in a state with a sales tax of 15%, so that's charged on top. That's why it's called "added sales tax", it's a tax added to the item price. You pay the store 72.99 * 1.15 = 83.94 dollars, and they will pay the 15% sales tax (10.95) to the state, and only keep 72.99.

Just to add to Ed's answer - States, cities, and even neighborhoods can have their own sales tax and different tax amounts on every item. Unlike VAT (which is, I believe 20% for the whole country), tax where I live is 10.1% for most things (it is higher or lower for certain items). If I drive an hour away, it can be as low as 8.5%. Also, it can change at any time if a city decides to add more tax. So, when you are in a store, if you see a price on a tag, it does not include the sales tax. When you pay for the item, the sales clerk tells you how much you actually need to pay to take the thing home. To the best of my knowledge, no one is at 15%. The highest sales tax in the country is around 10.5%. We also don't call it AST; it is just "sales tax."

In the US, states are able to apply sales tax on certain items. Prices are advertised without the sales tax. So, sometimes people ask a sales person "how much is it "WITH" the sales tax? We usually say "tax" or "sales tax". I have never seen or heard anyone call it an "added" tax. I think the dialogue is trying to apply the word from other countries with "value added tax". Each state can decide how much the sales tax is. Usually it is between 0-8% depending on the state. So if you buy an item for 1.00, when you go to pay at the register, they will add the state's % .. so you may pay from 1.00-1.08 depending on the state.