Any locality may establish a system for the retirement of injured or superannuated officers and employees; the members of the local police and fire departments; the public school teachers and other employees of the local school board; and the judges, clerks, deputy clerks and other employees of the judicial system; or any of them; and may establish a fund or funds for the payment of retirement allowances by making appropriations out of the local treasury, by levying a special tax for the benefit of such fund or funds, by requiring contributions payable from time to time from such officers, employees, members of police and fire departments, teachers, judges, clerks, deputy clerks and other employees of the judicial system, or by any combination of such methods, or by any other method not prohibited by law; provided that the total annual payments into such fund or funds shall be sufficient on sound actuarial principles for the payment of such retirement allowances therefrom. The benefits accrued or accruing to any person under such system shall not be subject to execution, levy, attachment, garnishment or any other process whatsoever nor shall any assignment of such benefits be enforceable in any court.