The difference between 100% nitrogen and the 79% nitrogen you've already got is so trivial that only racers actually get an advantage from the practice.
Think of it this way: does the outside of a rubber tire need to be in 100% nitrogen?
Guess what - the outside is exposed to lots more oxygen than the inside, because the trivial amount of ozone on the inside gets absorbed by reacting and then it stops, while the outside is constantly bathed in fresh oxygen and reactive ozone, and UV radiation besides.
Don't waste your time or money - any advantage of nitrogen-fill is so small as to be theoretical and unmeasurable in actual use, particularly in a car that is limited to 93mph. (For my [theoretical] 200mph Tesla Roadster I'd insist on nitrogen...)