This is one of most successful selling tools in retail - upselling. In business, the big problem is to sell someone something, once they have agreed to buy one thing, then often it is not that hard to sell them more. That is why so many places have loss leaders which is a product or service that is sold often at a loss in order to attract new customers to sell additional products and services to them.
But it does not have to be a loss leader, my Mum serving in the shop when a person brought something to the counter would say, "Would you like something else? We have many fine items here!" and pointed to a small pile of items on the counter where we had our top sellers. She did it because a few did buy more.
If you know your top-selling items, which is easy to find from your top-selling reports in our point-of-sale system, you can do this too.
Experiment and try it out. If you do it right many of your customers could be buying two items instead of one.