In response to customer complaints about rising prices of food items, a supermarket responds by making the following offer: For every $10 of purchase, the customers will earn $1 worth of coupons and this way they will end up making twice as much as the supermarket. If the supermarket makes $500 worth of total sales to all customers taken together, how much will it need to restrict its costs to so as to honour the offer?

Please provide the necessary working and statements if applicable and all figures should be round off to the nearest decimal places.