(1) In any contract for the construction, repair, alteration or demolition of any building, structure or facility awarded by the State of Mississippi, or any agency, unit or department of the State of Mississippi, or by any political subdivision thereof, which contract provides for progress payments in installments based upon an estimated percentage of completion with a percentage of the contract proceeds to be retained by the state agency, unit or department, or by the political subdivision or contractor pending completion of the contract, such retainage shall be five percent (5%), and the amount retained by the prime contractor from each payment due the subcontractor shall not exceed the percentage withheld by the state, or any agency, unit or department of the state, or by any political subdivision thereof, from the prime contractor. For the purposes of this section and Section 31-5-15, the term "retainage" means that money, or other security as agreed to by the parties to a construction contract, earned by the contractor, subcontractor or lower-tier sub-subcontractor or supplier, as the case may be, for work properly performed or materials suitably stored if payment for stored materials is provided for in the contract, which has been retained by the owner conditioned on final completion and acceptance of all work in connection with a project or projects by the contractor, subcontractor or lower-tier sub-subcontractor or supplier. On any contract as described herein, of which the total amount is Two Hundred Fifty Thousand Dollars ($250,000.00) or greater, or on any contract with a subcontractor, regardless of amount, five percent (5%) shall be retained until the work is at least fifty percent (50%) complete, on schedule and satisfactory in the architect's and/or engineer's opinion, at which time fifty percent (50%) of the retainage held to date shall be returned to the prime contractor for distribution to the appropriate subcontractors and suppliers. Provided, however, that future retainage shall be withheld at the rate of two and one-half percent (2-1/2%).