Section 162D. Any insurer issuing or delivering in the commonwealth either motor vehicle policies or bonds, as defined in section thirty-four A and thirty-four O of chapter ninety, which do business in the commonwealth through independent licensed insurance agents pursuant to the so-called American Agency System or any other system, other than that of an employer to employee relationship and designated producers, under the plan for equitable apportionment among companies of premiums, losses or expenses, or any combination thereof, as provided under section one hundred and thirteen H, shall pay each agent the indicated expense premium commission as established by the commissioner in his opinion, findings and decision on automobile insurance rates as commission only, and no portion of the indicated expense premium commission shall be considered as profit sharing or expense reimbursement. The insurer shall be allowed a variation in the commission paid to each agent of not more than plus or minus ten per cent of the dollar commission established in the commissioner’s findings; provided, however, the insurer shall be required to pay to its agents all of the commission dollars allowed in the rates as commissions. Nothing in this act shall prevent any insurer from paying any additional compensation in the form of commission overrides, bonuses, profit sharing benefits and expense reimbursements.