The town of Johnston may, by resolution or ordinance adopted by the town council, provide for a system of classification of taxable property as follows:
(1) Class one: all residential real estate that consists of not more than five (5) dwelling units;
(2) Class two: all commercial and industrial real estate and all residential real estate that consists of six (6) or more dwelling units;
(3) Class three: all ratable tangible personal property; and
(4) Class four: all motor vehicles and trailers subject to the excise tax created by chapter 34 of this title.