It's not my intent to be rude or unnecessarily redundant and I really hope you won't take offense at the directness of my response, however; those sentiments contains some of the most fundamental examples of why PCI compliance exists in the first place.
There are so many legitimate resources regarding the storing of CC/customer data, PCI DSS, merchant rules and regulations, and third party processing services, that continuing to seek an answer in a WordPress forum seems odd, or even a little suspect at this point.
Certainly, if you are the compliance officer for your business, you must already have some excellent sources of information that can point you toward the resources necessary to correctly answer your questions, and help custom tailor a solution for your unique situation.
No offense taken and it's not rude at all - I appreciate you trying to help.
The issue is that my POS system is a completely closed system, meaning that if I have an online store selling gift certificates it will be totally discrete from my POS.
This would mean managing two separate client databases, one of which is absolutely useless to me when a client comes in to redeem that gift certificate (We are a day spa and all client data needs to be in my POS system so we can track their treatment history, medical history etc).
So if I have to use a 3rd party credit card system there is no way, apart from a painstaking manual process someone having to enter all those client's details in to my POS system, but even then my POS will have none of the payment details, so to find out how much is on a given gift card, i would then have to look on the online database for their purchase.
Do you see the issue? It's nothing untoward or criminal - It's just a case of trying to be efficient and not using two entirely separate systems to manage payment and client info.
If there was some way of just securely taking credit card details without charging, these could then be manually inputted and charged each day in to my POS system. That way, the details would be secure and i would just have one system for all purchases.
Finally, even as the PCI compliance officer, i don't know a lot about online PCI compliance as we have one credit card terminal which is in a physical location. We've never had to deal or look in to online PCI before.