I've run into some pushback from clients because the US tax is not added to the total when a product is purchased. They don't like including tax into the price because they either have to reduce the price of their product to compensate for the added tax or their product price is too high, making them higher than their competitors.
Recently, I came up with a solution that is not ideal but it was adequate until the feature gets added. Since they were doing flat rate shipping, we added the tax to the shipping then labeled the shipping as "Flat Rate Shipping + Sales Tax"