The commissioner may adopt such rules as are necessary to enforce the terms of this agreement, which shall be exempt from the provisions of N.H. Rev. Stat. Chapter 541-A and shall have the effect of law, and which shall provide for each of the member states or agencies to collect tolls and perform audits on behalf of the other member states or agencies. Nothing in this section shall be construed to authorize the adoption of rules which alter any existing or establish any new tolls, fees, penalties, or interest charges; provided, however, that the rules may include tolls, fees, penalties, or interest charges which are otherwise provided for by the laws of this state.