Half of the scenarios you noted are not ones I have ever heard of (and I would bet are totally made up). Why would WalMart shoppers be exempt from sales tax?

You are right that advertising price with tax may be unreasonable. That does not preclude the store from putting the price with tax on the shelf. Out of all the scenarios you described, the only one that this would not cover is having an item be taxed differently if bought in conjunction with another item, but that can be noted in the same way that stores note a bundle or a bulk sales price ($1 each or 5 for $4).

There is difficulty in the case of a charge in tax rate (how often do those happen? Once every few years) or if there is a tax holiday (I see plenty of clothing stores have a sign for "15% off the marked price"). Those can be handled by having computer controlled shelf prices, which have existed for at least 20 years but never caught on much.