Even taxes should be included in prices.
And this has to be a top-down, legal thing, rather than something companies can opt-in to, because I think the business consequences of being the only one in your industry with transparent pricing would generally be lethal, and I've heard stories of restaurants going out of business due to including taxes in their prices. People want to pay less, and they'll go to the place they think will charge less. So this has to be enforced top-down.