Beginning on December 15, 2018, and each December fifteenth thereafter, the department shall cumulatively adjust the brackets in § 12-6-510 using the Chained Consumer Price Index for All Consumers, as published by the Bureau of Labor and Statistics of the Department of Labor, pursuant to Internal Revenue Code Section (1)(f). However, the adjustment may not exceed four percent a year, and notwithstanding the rounding amount provided in (1)(f)(7), the rounding amount is ten dollars. The brackets, as adjusted, apply instead of those provided in § 12-6-510 for taxable years beginning in the succeeding calendar year. Inflation adjustments must be made cumulatively to the income tax brackets.