The right to any pension, annuity, allowance, or benefit; to the return of contributions; to a pension, annuity, allowance or benefit itself; to any optional benefit, or any other right accrued or accruing to any person under this chapter; and to moneys under this chapter shall be exempt from any tax imposed by this state, county, municipal, or other political subdivision, except as provided in Code Section 48-7-27; exempt from levy and sale, garnishment, attachment, or any other process whatsoever; and shall be unassignable unless otherwise specifically provided for in this chapter.