Any general obligation bonds or revenue bonds shall be sold at public or private sale for not less than the principal amount thereof and accrued interest at a price which will not result in a net interest cost to the municipality of more than six per centum per annum computed to maturity according to standard tables of bond values. Nothing herein contained shall be construed as permitting the sale of bonds for other than lawful money of the United States of America.
NMS § 5-5-18