In Shopify POS, you can apply discounts when you've added items to the cart. You can apply a discount to the whole cart or individual line items.
If you have locations with a POS Pro subscription and use an iOS device, then you can apply any automatic discounts you create to those locations.
To allow your staff to use POS discounts, give your staff permissions to Apply custom discounts or Apply discount codes. Learn more about POS staff permissions.