Each employee who is a member of the retirement system shall pay to the county or have picked up by the county a sum equal to four and one-half percent of his or her compensation for each pay period. The contributions, although designated as employee contributions, shall be paid by the county in lieu of employee contributions. The county shall pick up the employee contributions required by this section for all compensation paid on or after January 1, 1985, and the contributions so picked up shall be treated as employer contributions pursuant to section 414(h)(2) of the Internal Revenue Code in determining federal tax treatment under the code and shall not be included as gross income of the employee until such time as they are distributed or made available. The county shall pay these employee contributions from the same source of funds which is used in paying earnings to the employee. The county shall pick up these contributions by a compensation deduction through a reduction in the cash compensation of the employee. Employee contributions picked up shall be treated for all purposes of the County Employees Retirement Act in the same manner and to the extent as employee contributions made prior to the date picked up.