Each participating employer may pick up the member contributions required by section 7-440 for all compensation earned on and after January 1, 2002, and the contributions so picked up shall be treated as employer contributions in determining tax treatment under the Internal Revenue Code of 1986, or any subsequent corresponding internal revenue code of the United States, as from time to time amended, and chapter 229. The employer shall pay such member contributions from the same source of funds that is used to pay the member. The employer may pick up such contributions by a reduction in the cash salary of the member, or by an offset against a future salary increase, or by a combination of a reduction in salary and offset against a future salary increase. If member contributions are picked up, they shall be treated for all purposes of the Municipal Employees’ Retirement Fund in the same manner and to the same extent as member contributions made prior to the date picked up. Municipalities participating in fund B may adopt this section for their members. Such election shall be made in a manner prescribed by the Retirement Commission.