(a) Except as otherwise provided in this Constitution, the power of taxation over the whole state may be exercised for any purpose authorized by law. Any purpose for which the powers of taxation over the whole state could have been exercised on June 30, 1983, shall continue to be a purpose for which such powers may be exercised.
(b) Subject to conditions and limitations as may be provided by law, the power of taxation may be exercised to make grants for tax relief purposes to persons for sales tax paid and not otherwise reimbursed on prescription drugs. Credits or relief provided hereunder may be limited only to such reasonable classifications of taxpayers as may be specified by law.