Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 94, § 295E

The price posted on any pump or other dispensing device from which motor fuel is sold, as required by section two hundred and ninety-five C, shall remain posted thereon and continue in effect thereat for a period of not less than twenty-four consecutive hours. No retail dealer shall sell motor fuel at any price other than the price so posted at the time of the sale. No premiums, rebates, allowances, concessions, prizes or other benefits shall be given directly or indirectly by any retail dealer so as to permit any purchaser to obtain motor fuel from such retail dealer at a net price lower than the posted price applicable at the time of the sale. In no transaction in which a retail dealer may fix or set a single price or charge for the sale of a quantity of motor fuel, together with some other commodity or service, shall such single price or charge be less than the aggregate of the charge, in accordance with the posted price, for the motor fuel involved in the transaction, plus the charge for such other commodity or service when the same is sold or rendered separately, rather than in combination with the sale of motor fuel.

Any retail dealer who sells and delivers motor fuel to a customer from a dispensing device, shall return the quantity indicator on the meter face to zero before each delivery by either automatic or manual means. A retail dealer shall not set the price indicator on the meter face of the dispensing device at a price per gallon higher than that posted on the dispensing device. Whoever violates any provision of the preceding two sentences shall, notwithstanding any contrary provision of section two hundred and ninety-five K, be punished by a fine of fifty dollars for the first offense and by a fine of one hundred dollars for each subsequent offense. The provisions of the first sentence of this paragraph shall not apply to motor fuel which is dispensed from a self-service pump operated by a customer.