175.221  Lump-sum payment of small retirement income.--Notwithstanding any provisions of the plan to the contrary, if the monthly retirement income payable to any person entitled to benefits hereunder is less than $30, or if the single-sum value of the accrued retirement income is less than $750, as of the date of retirement or termination of service, whichever is applicable, the board of trustees, in the exercise of its discretion, may specify that the actuarial equivalent of such retirement income be paid in a lump sum.