The employees of any city creating a fund and board in accordance with this subchapter shall pay monthly to the board an amount equal to 2% of their monthly salaries or wages and, if council elects by ordinance to make payments, an additional amount not to exceed 1% if deemed necessary by council to provide sufficient funds for payments to the surviving spouses of members who were retired on pension or killed in service, which shall be applied to the purposes of the fund. Payment of the monthly amount or contribution under this section shall cease and be discontinued at the time the beneficiary receives their pension. If, for any cause, an employee contributing to the fund ceases to be an employee of the city before the employee becomes entitled to a pension, the total amount of the contributions paid into the fund by the employee shall be refunded to the employee in full, without interest. If an employer returns to the employee the amount contributed and reenters the employ of the city, the employee shall not be entitled to the pension designated until 20 years after reemployment, unless the employee shall return to the fund the amount withdrawn, in which event that period of 20 years shall be computed from the time the employee first enters the service of the city. In the event of the death of an employee before the employee becomes entitled to the pension, the total amount of contributions paid into the fund by the employee shall be paid over to the estate of the deceased employee.