I thought the final comma was optional -- that the rule was either way, but be consistent. I plugged it in because I believe it facilitates clear communication.
Now I've learned that the only style guide that advocates leaving it out is the Associated Press Stylebook. The rule according to all other authorities requires that final comma.
We don't write newspaper articles. We write grant applications. So there! My instincts were right for a change. (Generally, I don't trust my grammar or punctuation. I'm forever looking things up.)
For a more authoritative discussion than this:
The Case of the Serial Comma--Solved!: "My original assertion stands, with minor qualifications: Except for journalists, all American authorities say to use the final serial comma: 'He went to the store to buy milk, butter, and eggs.'
The reason for the final serial comma is to prevent the last 2 items' being confused as a unit (butter-and-eggs)."