The phrase "of sales" is a prepositional phrase that indicates the context or purpose of a particular action, in this case referring to the act of selling something. Full definition
He told the deputy governor about some of the committee's recommendations including the use of Points of Sales in collecting revenue. (punchng.com)
It will help stop traffic from large brokers of puppy mills to supply stores that too often have proved to be unacceptable points of sale for puppies. (sandiegouniontribune.com)
A few years ago, one of my colleagues spoke with a senior vice president of sales who recently had visited a satisfied long - time client. (entrepreneur.com)