Online you’d need to input your address before ever seeing pricing which I personally don’t care for. In-store would be easier from that perspective but there are so many exemptions and jurisdictions it would take a ton of work to switch over. Some tax code would have to be rewritten. Possible, but far more work than what the FTC is currently talking about.
An example of one of these complexities. In 13 states, sales tax is collected on a Milkyway but not a Twix.