The county board of any county in the State of Nebraska is hereby empowered to issue coupon bonds of any denomination, as it deems best, sufficient to pay the outstanding and unpaid bonds, warrants, and indebtedness of such county. The county board of any county may limit the provisions of sections 10-501 to 10-509 to any fund or funds of the county. No bonds shall be issued to a greater amount than three and five-tenths percent of the taxable valuation of such county, and the county board shall first submit the question of issuing bonds to a vote of the qualified electors of such county.