Quantity discounts with different discounting schedules for different products based on purchases of specific quantities.
Case discounts are configured on a product by product basis. The product editing screen (Admin->Catalog->Categories/Products->Edit) has settings for Case Discounts just below the pricing fields.
Filling in a Case Size of 12 and a Case Discount of 10 Dollars Off would produce a $120 savings for a purchase of 12 or 13 of this product.
Because Case Discounts is an Order Total module, the discount is shown on the payment page of checkout.
If you use Discount Preview, the Case Discount is visible on the shopping cart page.
NOTE: This software is not sold without installation. Installation is included in the price.