Here is tidbit: sales taxes are an obligation on the company or business doing the sale. It is not a purchase tax. The purchaser is merely charged by the company to cover the tax. We have foolishly sort of informally agreed that the purchaser is responsible for the tax because the seller gives his item price and them shows the tax that is added. We really need to stop this custom.
If the phone company has advertised service for $35 then they should be taken to court and made to honor this price. The phone company is responsible for the tax, not the customer. They should have included the tax in the advertised price.
Good point. When I do shows, I set a price and don't dicker about with the sales tax. That's my problem to figure out later. It truly helps with sales. That, and round numbers.