Official comment
Hi Laura ... you can have ONTRAPORT log the transaction! Set Zapier to add a Tag to the contact, then have a global Rule that looks for that tag to be added and adds the product to the Purchase History. Here's an example:
I have a product named "Coffee" and a Tag named "Customer: Coffee". The following global Rule is created in Contacts > Rules:

The Tag "Customer: Coffee" is added to my contact Isaac Newton, and the Rule runs and adds the product purchase to his history.
Note that the Rule uses the price set for the product in Sales > Products.
The sale will be reflected in the sales reports, Dashboard metrics, etc.