The director of finance shall also exercise the powers conferred and perform the duties imposed by general law upon county treasurers, and shall be subject to the obligations and penalties imposed by general law. All moneys received by any county officer or employee for or in connection with county business shall be paid promptly into the hands of the director of finance. All such money shall be promptly deposited by the director of finance to the credit of the county in such banks or trust companies as the board selects. No money shall be disbursed or paid out by the county except upon checks signed by the chairman of the board, or such other person the board designates, and countersigned by the director of the department of finance. The board may designate one or more banks or trust companies as a receiving or collecting agency under the direction of the department of finance. All funds so collected or received shall be deposited to the credit of the county in such banks or trust companies as the board selects. Every bank or trust company serving as a depository or as a receiving or collecting agency for county funds shall be required by the board to give adequate security therefor and to meet such interest requirements as the board may by ordinance or resolution establish. All interest on money so deposited shall accrue to the county’s benefit.