Any person with a legal interest in real estate upon which a real estate tax lien has been executed may make partial payments in redemption to the collector of taxes who shall receive the same and give a receipt therefor. The collector shall pay over such sums to the town treasurer. If complete redemption is not made before a deed of the real estate is given to the lienholder, the collector of taxes shall within 10 days direct the selectmen to issue an order upon the town treasurer to refund to the person making such partial payments or his heirs or assigns the sum so paid. The selectmen shall promptly issue such order. If the order is not issued within 30 days of the time the collector directs that the order be issued, the sum to be refunded shall draw interest at the rate of 6 percent per annum from the date the sum was directed to be paid to the date of actual payment.