Closed shop sale

Purchase of 5 or more items 15% discount.
Purchase of 10 or more items 20% discount.
Purchase of 20 or more items 25% discount.
Purchase of 30 or more items 30% discount.
Purchase of 40 or more items 35% discount.
Purchase of 50 or more items 40% discount.
Purchase of 60 or more items 45% discount.
Purchase of 70 or more items 50% discount.