They could be major in your local area and go through multiple states but the big ones ending in 0 or 5 tend to go across the country. And I-80 and i-95 would fall into that category, if those roads stay in a lower tier or get expanded later is another story.

I think it is usually multiples of 10 as well so for example I-5 runs from the border in San Diego (or close enough) to the border with Canada. I-10 runs from LA in California to Jacksonville Florida, smaller routs ending in 2, 4, 6, or 8 are small sections that terminate a few towns over usually or connectthe bigger highways to eachother.