Not only banks but countless other services and businesses. Stock markets change minute to minute. Cryptocurrency changes by the minute. Heck even a grocery store has thousands of items that change from day to day and they seem to manage to list current prices all the time. In Canada they even guarantee the price is correct or get the item free or $10 off if item is more then $10. So I think everyone can see this excuse is a non issue.
Grocery stores do not advertise with tax-inclusive prices, in fact the opposite. Heck, I live in a no-sales-tax state and even then, some items might still be taxed because they are considered "prepared foods" and fall under hospitality taxes, so the shelf price and total at the register may not be the same.
