There are currently no actual fields for discounts.
However, you could create a discount field in the COST OF SALES section (when adding a sales product)
and the calculation would be done each time there is a sale.
Company Inc sells Product A for $100.00. They want the product to carry a 15% discount.
A "Discount" field (carrying a 15% rate) is added in the "Cost of Sales" section when adding a sales product.
Therefore, the profit from a sale of Product A will be $85.00 before cost of goods sold.
($100.00 x 15% = $15.00... ---> ... $100.00 - $15.00 = $85.00)