Heritage collecting Sales Tax is likely something they would rather not have to do. It's a money losing proposition. Likely cost them plenty on the accounting end, and any fees that any merchant processing company deducts from that portion of sales, is a direct loss, since you can't charge somebody a collection fee on top of the sales tax collection.
Unless (to get on my own soapbox
), you are Ebay, and you've figured out how to charge what's essentially a "Sellers Fee", on the entire sale, including Shipping and any collected Sales Tax. The higher a states sales tax rates are, the more money Ebay collects for itself, for that transaction.