What the Price Tag Doesn't Say
A price tag looks like a simple thing. It is not.
In most of Europe, the price on the shelf is the price you pay. The tax is already inside it, because shops are required by law to show shoppers the final amount. Japan works the same way. In the United States, the number on the shelf is usually the price before tax, and the tax is added at the checkout. It is set by each state, and often by the county and the city as well, so the same shirt can cost slightly different amounts in two towns forty minutes apart. In a few states there is no sales tax at all.
A visitor from Hamburg who orders a coffee in Chicago hands over the exact number printed on the board, and is politely asked for more. Nobody has cheated anybody. The two countries simply print different facts.
Neither system is an accident, and each one is defended with the same word: honesty.
The argument for putting the tax inside the price is that shopping should not require any mathematics. If the tag says nine, you need nine. Prices can be compared directly, advertised prices are true, and nobody is surprised at the checkout. That matters most to the people counting coins, who can least afford a surprise.
The argument for adding it at the end is that a hidden tax is a tax nobody argues about. If the tax is folded into the price, most shoppers will never know what they paid, and it can be raised quietly. If it is printed on the receipt as a separate line, every shopper is reminded, several times a week, of exactly how much the state is taking. And where those rates are set locally and changed often, the separate line is practical as well: one national price label would be impossible.
So both sides are right about something. The European receipt protects you from surprise; the American receipt protects you from forgetting. What each system makes easy, the other makes invisible.
The next time a price surprises you in another country, the surprise isn't really about money. It is about which fact somebody decided you should see.