That is true , not only in US but in almost every country tourist are tax free (not for food items). Ppll use it mostly for electronics and jewelery. At the time of purchase you have to ask for special receipt to be presented at tax return office at the airport. In most of the airport this is after check in. If you want to get the tax return you have to make sure that the shopkeeper gives you this special receipt. some shopkeepers may not know it. It is not the ordinary receipt. Shopkeepers usually see your passport before issuing you this type of receipt.