The board of supervisors shall pay all lawful fees of the chancery clerk and its attorney now prescribed by law, which fees are incidental to the execution of said refunding bonds, and may also pay all expenses in connection with the validation of said refunding bonds and procuring the opinion as to the validity thereof from some expert bond attorney, other than the state bond attorney, of national reputation. However, in cases where the bonds to be refunded are not due or redeemable prior to maturity, such board in procuring the surrender of such outstanding bonds may expend not exceeding an additional two and one-half percent (2 ½%) of the principal amount of refunding bonds actually issued and delivered, but in no event shall any part of the said two and one-half percent (2 ½%) be used in the payment of attorney’s fees. All such fees and compensation shall be paid out of the interest and sinking fund applicable to the bonds to be refunded, if the amount credited to such fund be adequate therefor. Otherwise, such fees and compensation shall be paid out of the proceeds of a special annual tax to be levied for that purpose by the board of supervisors upon all taxable property within such county. All expenses as authorized by Sections 65-33-61 through 65-33-71 in effectuating the exchange of said bonds and the actual expense of the state treasurer in paying principal and interest on said bonds shall be paid by the board of supervisors of the county.