At the time appointed, the board of directors shall open the proposals, and may sell the bonds or any portion thereof to the highest responsible bidder or bidders. Any and all bids may be rejected and no proposal shall be accepted unless accompanied by a certified or cashier’s check for such reasonable percentage of the amount of the bid as shall be determined by the board of directors, to apply to the purchase price of the bonds. The amount of such check shall be forfeited if, after the acceptance of the proposal the bidder refuses to accept the bonds and to complete his purchase thereof on conditions stated in his bid. In case no award is made the board of directors thereafter may again advertise the bonds or any part thereof for sale.