(a) The proposed rate for the district sales and use tax imposed under Subchapter B, Chapter 321, Tax Code, may be any rate that is an increment of one-eighth of one percent, that the municipality determines is appropriate, and that would not result in a combined rate that exceeds the maximum combined rate prescribed by § 321.101(f), Tax Code. The proposed rate for the district sales and use tax imposed under Subchapter B, Chapter 323, Tax Code, may be only:
(1) one-eighth of one percent;
(2) one-fourth of one percent;
(3) three-eighths of one percent; or
(4) one-half of one percent.
(b) A sales and use tax approved under this chapter may be charged in addition to any other sales and use tax authorized by law and is included in computing a combined sales and use tax rate for purposes of any limitation provided by law on the maximum combined sales and use tax rate of political subdivisions.

(c) A municipality that creates a district shall adopt a sales and use tax under § 321.108, Tax Code, for financing the operation of the district.