There is zero reason that can't be on the price tag.

None of these a reasons the store, which posts it's own prices and barcodes, can't just include the total on the tag, or better yet set the price to the nearest whole number (or division of .10/.25) and take the tax out of that full amount. I know because I live in the midwest, I worked in retail/grocery store and our store piloted a test program of doing exactly that. Customers were incredibly happy and our overall sales actual went up because people who didn't normally shop with us started to because it was easier to budget.

We got shut down by corporate beancounters who were freaking out because we were supposedly making less money. Except our sales and profits were up for the 8 weeks we demo'd the program and 4 weeks after we were forced to stop sales dropped below our year-on-year average. Literally forced to stop a program that benefited the customer and retailer because corporate greed couldn't tolerate the customer not being screwed.

And counties that have their own sales taxes. So not even within the state is the rate the same.

So does Europe.