(a) Each retailer in a municipality that has adopted a tax authorized by this chapter shall add each sales tax imposed by the municipality under this chapter and by Chapter 151 to the sales price, and the sum of the taxes is a part of the price, a debt of the purchaser to the retailer until paid, and recoverable at law in the same manner as the purchase price. If the municipality imposes the tax on gas and electricity for residential use, only the municipal tax is added to the sales price of sales of gas and electricity for residential use.
(b) The amount of the total tax is computed by multiplying the combined applicable tax rates, or the rate of the municipal tax only for sales of gas and electricity for residential use in a municipality that imposes the tax on gas and electricity for residential use, by the amount of the sales price. If the product results in a fraction of a cent less than one-half of one cent, the fraction of a cent is not collected. If the fraction of a cent is one-half of one cent or more, the fraction shall be collected as one cent.

(c) The comptroller may publish schedules and brackets of amounts of taxes based on the formula provided by Subsection (b) for use in municipalities that have adopted the taxes authorized by this chapter.