Such bonds shall be issued and sold from time to time after their date to the highest bidder for cash at not less than par and in such denominations as the officials shall determine. They shall bear interest at a rate not exceeding five per cent per annum, payable semiannually, and to each bond shall be attached coupons for the semiannual interest from date to maturity. Such bonds shall be signed by the chairman of the governing body of the county or mayor of any town or city, and the lithographed signature shall be a sufficient signing of the coupons on the bonds.