Hi there, @robinpaolotan,
Let's use the Automatic Discounts feature so you can set up a discount on your selected items. This feature allows you to select items and define discount pricing automatically applied to your sorting.
I've also added this article for additional information about QuickBooks POS: QuickBooks POS Customer Resource Center: Videos.
Feel free to update this thread if there's anything else you need with setting up item discounts. I'm always around here in the Intuit Community to help.