I mean, there are countries where tourists don’t have to pay tax on top of items (meaning they pay for it tax free given if they presented their passport upon purchase proving they’re merely only a visitor, that won’t work on expats though). There are countries who have tax refunds when visitors are leaving (basically reclaiming VAT whilst at the airport), they have already purchased the goods with VAT paid but gets refunded upon them departing.
Sales tax in the US is also not a VAT. And every state and municipality are free to have their own rules. My town where I live and the next one over have different sales tax rates (on top of state sales tax), which is part of the reason why it won’t be on the price tag. It’s just not practical.
I fundamentally disagree that it is impractical not to put it on the price tag. Every store prints their own price tags and puts them either directly on the item, or on the shelf. It wouldn’t be hard to just make that price different to reflect the tax. We already do it with gasoline.
Every POS is also calculating those taxes anyway to print on your receipt. The only reason prices on tags don’t include tax is because it’s not required and smaller number is better.