Here's a little link I found that details the tinting laws in all states. It says NJ doesn't allow any tinting on the front side windows. Installers will put whatever you ask for, but the cops might think differently about your choice. I live in AZ so if I get pulled over for my tint being too dark (which it legally is...
) I get a 30-day notice (Fix-it Ticket) to get it squared away. You didn't mention which windows you are planning to tint, but you might wanna ask Johnny Law (or someone in the know) before you go to the expense of doing the front windows.
New Jersey Window Tint Law - TintCenter.com
Good Luck and post some pics when you get'r done!