A member is entitled to credit in the retirement system for each month of unused sick leave, as certified by the employer, if the member or the member’s employer pays an amount equal to the member’s final average salary, times the number of months of sick leave converted, times the employer and employee contribution, plus the required contribution for the retiree health benefits program. Hours of sick leave equal to a fraction of a month are deemed to be a full month for purposes of conversion to service credit. A member may convert all of the member’s certified sick leave or a part of that person‘s certified sick leave.