Hello Sean, Ben here - your Shopify Guru!
There are a couple apps that can provide you with great flexibilty when incentivising your customers with discounts and promotions. Some of the most popular ones are:
These can all provide pop ups when customers are adding products to the cart, offer special deals when they click checkout, etc.
We also have apps specifily for when customers are exiting your site:
Be sure to check these apps , I hope this helps! Feel free to reach out if you have any further questions :)
Cheers,
Ben Czegeny - Shopify Guru
Support@Shopify.com