Tennessee Code Title 5. Counties § 5-3-118

(a) The governing body may sell any or all of the bonds authorized under §§ 5-3-113 -- 5-3-121 in such manner and for such price as it may determine to be for the best interests of the unit, but no such sale shall be made at a price so low as to require the payment of interest on the money received therefor at more than six percent (6%) per annum, computed with relation to the absolute maturity or the average maturity of the bonds, in accordance with standard tables of bond values.

(b) Any or all of the bonds authorized under §§ 5-3-113 -- 5-3-121 may be exchanged for the bonds to be refunded thereby, or the evidences of indebtedness to be funded thereby, including bonds not matured or redeemable, if the holders thereof be willing to surrender the same for retirement.