We don't integrate but we have an API so if you have your own developers they could program your own integration. Alternatively, our receipt reports export to CSV/Excel so this can be used to upload and import into an accounting system which is what most of our customers do.
Although we don't have any POS integrations at the moment, we are looking at a couple of options. One is Stripe:
And the other is Paw Payments:
I think we will most likely be integrating with paw payments because they boast they are cheaper than the other POS systems as they deal with Not For Profits and want to reduce costs as much as possible.
For more information, contact firstname.lastname@example.org