(1) Upon receipt of the cost figures required by section 66-4,143, the department shall determine the statewide average cost by dividing the total amount paid for motor fuels by the State of Nebraska, excluding any state and federal taxes, by the total number of gallons of motor fuels purchased during the reporting period.

(2) After computing the statewide average cost as required in subsection (1) of this section, the department shall multiply such statewide average cost by the tax rate established pursuant to section 66-4,144.

(3) In making the computations required by subsections (1) and (2) of this section, gallonage reported shall be rounded to the nearest gallon and total costs shall be rounded to the nearest dollar. All other computations shall be made with three decimal places, except that after all computations have been made the tax per gallon shall be rounded to the nearest one-tenth of one cent.

(4) The tax rate per gallon computed pursuant to this section shall be distributed to all licensed motor fuels producers, suppliers, distributors, wholesalers, importers, and compressed fuel retailers at least five days prior to the first day of any semiannual period during which the tax is to be adjusted. Such tax rate shall be utilized in computing the taxes due for the period specified by the department.