Cashiers are not allowed to offer random discounts, and bothering customers with purchase options that are not at all related to the items they are already taking might upset them.
Trying any of those will backfire and not help marketing products.
The cashier can upsell or cross-sell. This means you can:
Check out this short video on Cross-selling and Upselling to learn a bit more.
It takes only 3:16.
Photo by freepik on freepik
Reference: 14 Overlooked Cashier Skills to Grow Your Business by Anna Dizon on Fit Small Business