Nobody thinks anything is getting "padded" with sales tax other than Europeans who have never heard of the practice before and can't get over the fact that ~5% (the median US sales tax is 5.1%) wasn't disclosed as if that is making their breakfast unaffordable.
You're never required to tip so the "advertised price" and the price at the register are identical. You choosing to leave $2 on top of that doesn't change anything, even if it's only done through social pressure.
You're never required to tip so the "advertised price" and the price at the register are identical. You choosing to leave $2 on top of that doesn't change anything, even if it's only done through social pressure.