CVS is what is known as a Pharmacy Benefit Manager or PBM. (https://www.caremark.com/) I have access through my Medicare supplement insurer.
Yes, I do get my saline there sometimes - but I avoid it when possible because it is sent overnight in insulated containers, and that is a lot of packaging waste and shipping cost to be avoided - just drives up cost of care.
To anticipate the next question, I do not know if Caremark are available to the general public. But if you have health insurance with Medicare - either a Part B/Part D plan or an Advantage plan, you probably have a PBM. You need to look at the details of your plan.
Sue