Version 1.2 of Cart Viper the DNN ecommerce allows users to make donations, the user can choose to make the donation at the point of checkout:

make donation

Or the donation control can be accessed via a query string parameter, thus allowing you to link to the control directly in your standard portal menu. As with all controls used within Cart Viper, a customizable templating system is used giving you the flexibility to use this feature as you wish.

When configuring donations the store admin has the option to enter a number of predefined amounts for the user to pick from, or the user can enter their own amount along with a name that is associated with the donation:

donation page

It is worth noting that the user does not have to have an item in their cart they are able to checkout with just a donation in their cart. Furthermore orders that contain donations are viewable in the store and user interfaces as per standard orders.