Amen to that. As a business owner, I fully expect to be audited sooner or later, and things like this are a good way to get hefty fines.
Btw it depends on state law of course. In Europe we have VAT as you know so it is passed on through the chain to the final customer. That is very similar to you paying sales tax on the amount you tack on to shipping charge (if applicable). The end result of sales tax and shipping tax are very similar. The way I understood it, it is a different way of doing things.