In many US states the payment of sales tax for mail order or internet purchases is supposed to be paid by the buyer. It is only a pragmatic convenience that stores collect the sales tax at the time of sale, but it is still required for all sales. There is a place on the state income tax form to include such payments as should have been made.
I feel no sympathy for the likes of states that rely solely on sales tax - it is a regressive tax on the poor to the relative benefit of the wealthy.
Want to fix something - place the purchase of stocks and bonds under sales tax law.