I like doing mental math. I enjoyed it more (and more successfully) when I practiced in high school, but still figure out tax, tip, and the occasional oddly-precise trivia question (Wednesday-night Tavern trivia usually has a Nerd Round math question which results in an unusual fraction). But I rarely know how much I have to pay for something - anything! - until the bill arrives.
There are a lot of factors in prices - tax and certain fees are about the only thing the seller can't control. However they do know enough to calculate them at the time of sale. Yet AT&T will never even estimate your next total bill, just the "base price" of the plan they're sticking you with. Restaurants don't include enough to pay waitstaff a living wage. Car dealerships advertise prices that don't include "extras" like air conditioning. This is Texas: air conditioning is more critical than brakes.
Why is this burden on the consumer? Lemon laws put the burden of acceptable quality on the seller. Why not force sellers to list the true price? As a consumer, I don't care how much of the price is taxes, how much of it is fees, how much reflects the seller's cost. I need to know how much cash makes the bright shiny thing mine. Sellers, put the full price of the product (including features being shown) on advertisements at least as big as the company name. If it can vary, put a price that covers all situations or don't list the price. But if a price is on an ad, I should be able to go wherever you're advertising, and buy it right there for that much cash. If there's a price sticker on an item, that should be what the cashier asks for. This seems like a simple rule that keeps the burden of naming the price on the party that defines it.
As for tips, I like to tip for good service, and don't mind it for average service, but let's apply minimum wage (ideally a living wage) to all employees, so I don't have to keep bad waiters off food stamps.
What's wrong with a True Price system? It could affect marketing, but it affects all competitors equally. It could hide taxes, but those could still be broken out on the receipt - or even in the ads - just as long as the full price is also shown.