Regardless how sales tax is charged, the items can be priced to cover tax and sold at that price, tax included. Other parts of the world already do this, and it is the business that reports the numbers to the gummint and pays their tax bill. Profit margins can be optimised to fix the little sway in the sub-cent variance of percentages, and only a real penny pincher would care. You sell this much, you pay this much, every month. It’s how it works in the end.
And businesses already re-print/price their items frequently, sometimes on every purchase order received, which can be several times a week, because prices go up.