I see the justification in adding the tax on afterwards because putting it on stickers and menus imposes more work on the business whenever the sales tax changes. If you’ve ever done a store inventory you’ll get it. Also if you live in a place with sales tax, which in America means almost everywhere, you get used to mentally approximating it, or at least knowing it’s going to be added on - and a sales tax amount is mandated, it isn’t something you have to agonize over.