Nitrogen filled tires are somewhat of a placebo, there is a benefit but the cost is rather high for an on the road car.

Race car teams started to use nitrogen because high pressure nitrogen bottles are convenient where compressed air is not available. For a racing application, dry gas is critical in keeping tire pressures at expected levels. ( Water throws off the expansion curve )

Nitrogen is a larger molecule so tire leak rates will be lower but, if a tire is filled with regular air, eventually you will end up with a higher concentration of nitrogen / lower leak rate as the oxygen and other gasses leak out.

As an experiment, I used bottled CO2 to fill a slightly leaky tire, as the CO2 concentration rose, so did the frequency of refilling.

Regular dry air will be just fine.