There shall be a fund established by the Commonwealth Transportation Board, from the toll revenues described in this section, for the purpose of funding transportation improvements which are related to or affected by the toll road. Toll rates shall be set in multiples of five cents; however, the Commission shall order that that percentage of each toll by which the toll established exceeds that necessary to provide the operator with an amount necessary to meet the operator’s obligations under § 56-543 and earn a reasonable return shall be committed to the fund. In addition the operator, the Board, and the local governments through which the road passes may jointly petition the Commission to establish an additional toll amount to be committed to this fund.