The four things that get added at tender time, and the rules that go with them.

Discounts

• Item level discount and order level discount.
• Add a discount by code, or scan a discount code.
• Add customer information for a discount where the discount requires it.
• Employee discount.
• Delete a discount.

Gift cards

• Activate a gift card.
• Bulk gift card activation, either by range or by individual entry. Use range activation when a site takes delivery of a new card batch.
• Add value to a gift card.
• Check a gift card balance.
• Cash out a gift card where local rules require it.

Tips

• Add a tip to an active order, a saved order or a split payment order.
• Update a tip amount.
• Adjust tips from order history, for single payment and multi payment orders.
• The customer facing tip screen can be opened from the terminal.

Donations

• Add a donation to an order.
• Change the donation amount.
• Delete a donation.

Reference

Discounts, Gift Cards, Tips, Donations.

Source: Global Payments / Xenial Enterprise POS product documentation. Enterprise sites are heavily configured, so confirm the exact behaviour against the customer own build before advising a change.