Beginning July 1, 2015, and every other year thereafter, the gasoline tax shall be adjusted by the percentage of increase in the Consumer Price Index for all Urban Consumers (CPI-U) as published by the United States Bureau of Labor Statistics determined as of September 30 of the prior calendar year; said adjustment shall be rounded to the nearest one cent ($.01) increment, provided that the total tax shall not be less than provided for in section (a).
R.I. Gen. Laws § 31-36-7