In lieu of the tax rate computations required in Section 7-2-7 N.M. Stat. Ann., the secretary may adopt regulations requiring taxpayers to pay taxes in accordance with tax rate tables. The tax tables may be established either by regulation or by instruction but shall be computed substantially on the basis of the rates prescribed in Section 7-2-7 N.M. Stat. Ann.. The secretary may by regulation or instruction exclude from the application of this section taxpayers having net incomes in excess of an amount to be determined by the secretary and may exclude taxpayers in any net-income class having more exemptions than the number of exemptions specified by the secretary for that category.