(a) There is levied and imposed within the county gross receipts tax area in Morgan County, in addition to all other taxes, including municipal gross receipts license taxes now imposed by law, a special county privilege license tax paralleling the state sales tax, such privilege license tax to be determined by the application of rates against gross sales or gross receipts, as the case may be, and within specified areas at the rate of two percent of the gross proceeds of sales or receipts. (b) Provided, however, the tax rate shall be one-half of one percent for the gross sales or gross receipts:
(1)a. Upon every person, firm, or corporation engaged or continuing within this county in the business of selling at retail any machine, machinery, or equipment which is used in planting, cultivating, and harvesting farm products, or used in connection with the production of agricultural produce or products, livestock or poultry on farms, and the parts of such machines, machinery, or equipment, attachments and replacements therefor which are made or manufactured for use on or in the operation of such machine, machinery, or equipment, and which are necessary to and customarily used in the operation of such machine, machinery, or equipment; provided, that the one-half percent rate herein prescribed with respect to parts, attachments, and replacements shall not apply to any automotive vehicle or trailer designed primarily for public highway use, except farm trailers used primarily in the production and harvesting of agricultural commodities.
b. Where any used machine, machinery, or equipment which is used in planting, cultivating, and harvesting farm products, or used in connection with the production of agricultural produce or products, livestock, and poultry on farms is taken in trade or in a series of trades as a credit or part payment on a sale of a new or used machine, machinery, or equipment, the tax levied herein shall be paid on the net difference, that is, the price of the new or used machine, machinery, or equipment sold, less the credit for the used machine, machinery, or equipment taken in trade.
(2)a. Upon every person, firm, or corporation, engaged or continuing within the county in the business of selling at retail any automobile vehicle or truck trailer or semi-trailer.
b. Where any used automotive vehicle or truck or semi-trailer is taken in trade, or in a series of trades, as a credit or part payment on the sale of a new or used vehicle, the tax levied herein shall be paid on the net difference; that is, the price of the new or used vehicle sold less the credit for the used vehicle taken in trade.
(3) Upon every person, firm, or corporation engaged or continuing within this county in the business of selling at retail machines used in mining, quarrying, compounding, processing, and manufacturing of tangible person-al property; provided, that the term machines, as herein used, shall include machinery which is used for mining, quarrying, compounding, processing, or manufacturing tangible personal property, and the parts of such ma-chines, attachments, and replacements therefor, which are made or manufactured for use on or in the operation of such machines and which are necessary to the operation of such machines and are customarily so used.
(c) There are exempted, however, from this section and from the computation of the amount of the tax imposed in this section, the gross receipts of any business and the gross proceeds of all sales which are presently exempted under the state sales tax statutes from the computation of the amount of the state sales tax.