Best to ask your local building department....

Use a steel connector made for the purpose, especially if you ever anticipate high winds.

Everyone uses the gun nails, but if you're getting it inspected, ask. My inspector asked for the tie downs, then forgot about it.

@csacontest,

I infer from your description that you're stick framing the roof of your addition with rafters parallel to the ceiling joists. If so, Joseph Corlett's otherwise nice and colorful visual above doesn't apply; it shows a method for attaching a truss to a top plate which is quite different from a rafter-ceiling joist connection.

A 16d nail has a diameter of 0.165 inches; what you are proposing to use is a smaller diameter so it doesn't meet the prescriptive code requirements. However, the fastener manufacturer should have a report you can refer to which will gives the equivalent number of fasteners to meet the code requirement. Here's a sample:

https://www.bostitch.com/~/media/bostitch/files/building-code-report-pdfs/power-driven-staples-and-nails-2019.pdf

If you're an insomniac, you'll want to read the entire report in detail.