If I'm understanding right, your VAT (value-added tax?) would equal our 'sales tax.' There is no federal sales tax (yet) but each state can determine their own sales tax rate, or none at all. For instance, I live in the state of Idaho which has a 6% sales tax. If I drive across the border into Oregon, they have no sales tax.
For brick and mortar business, it is pretty straight forward, you pay the sales tax of the state you are in, or none if they have no sales tax. However on internet orders, you will usually pay no sales tax unless you live in the same state as the Vendor. If I buy a knife from Survive Knives, which is in my state, I pay an extra 6%. When I bought the M4 from collectorknives, I was not taxed extra as an out of state sale. With free shipping, I got it here for about one hundred twenty-one US dollars, an amazing deal on such a knife IMO.