Any person with a legal interest in real estate so sold may make partial payments in redemption in sums of $5 or multiples thereof 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 sold is given to the purchaser, the collector of taxes shall within 10 days direct the selectmen to issue an order upon the town treasurer to refund to that person making such partial payments or his heirs or assigns the sum so paid. The selectmen shall promptly issue such orders. 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.