If the district maintains its own retirement fund the retirement board shall have exclusive control of the administration, investment, and disbursement of such fund. Investment of the fund shall be subject to the terms, conditions, limitations, and restrictions imposed by the laws of this state upon savings banks in the making of investments by savings banks, and cash may be deposited in any licensed national bank or banks in this state or in any bank, banks, or corporations authorized or licensed to do a banking business and organized under the laws of this state.