The retirement system shall certify to each employer the proportion of each member's compensation to be deducted, and to facilitate the making of deductions the retirement system may modify the deduction required by a member of such amount as shall not exceed 1/10 of 1% of the compensation upon the basis of which the deduction is to be made.
There shall be credited in the annuity savings fund to the individual account of each member any amounts so deducted or contributed by him.