After August 7, 1965, every firefighter subject to the provisions of sections 35-201 to 35-203 as they existed prior to January 1, 1984, shall contribute to the city an amount equal to five percent of his or her salary until he or she shall be entitled to retire or otherwise become eligible for a pension. No such firefighter continuing in the employment of the city as a member of such department after becoming eligible to retire shall be required to make any further contribution. Any such firefighter whose employment shall terminate, whether by discharge or otherwise, prior to the time he or she shall become entitled to a pension, and who shall have made contributions from his or her salary as provided in this section shall, upon demand, be reimbursed by the city for the amount of such contributions plus interest at five percent per annum.