Each person engaging or continuing in the business of leasing or renting tangible personal property subject to the rental tax shall add to the rental price and collect from the renter or lessee the amount of tax owed by such renter or lessee. It shall be unlawful for any person engaging or continuing in the business of leasing or renting tangible personal property subject to the rental tax to fail or refuse to (1) add the rental tax to the rental price, and (2) collect from the lessee or renter the amount of tax required to be added to the rental price. It shall be unlawful for any person engaging or continuing in the business of leasing or renting tangible personal property subject to the rental tax authorized to be levied by this part to refund or offer to refund all or any part of the amount collected or to absorb or advertise directly or indirectly the absorption or refund of any portion of such tax. The rental tax authorized by this part shall conclusively be presumed to be a direct tax on the retail consumer, precollected for the purpose of convenience only.