You're completely missing the point.

It's not the price that's advertised that's fucking stupid - go ahead and advertise the price as $10 and let Americans imply that tax will be added on top of that. Add a sign out front that says $10 and let Americans imply that tax will be added on top of that. Mail out flyers listing the pre-tax price. Whatever, that doesn't matter. ** The stupid part is that the tax isn't added in each store.** It's not hard to simply list the price as $11 in one store, $10.50 in another store in a different state, etc. The price you see on the shelf is supposed to be how much money you need to exchange to purchase that item. Not a "rough ballpark figure" that you will only know for certain after you've agreed to purchase it. That's how the rest of the world works and it makes buying things sooooooooooooooooooooooooooooooooooooooooooooo much simpler.