A member upon retirement for service shall receive a monthly retirement allowance computed according to his or her completed years of service, as follows: Ten years, but less than fifteen years, three percent of his or her final average salary for each year of service; fifteen years and over, three and one-half percent of his or her final average salary for each year of service: PROVIDED, That in no case shall any retired member receive more than seventy-five percent of his or her final salary except as increased as a result of the cost of living increases as provided by this chapter.