IMHO, if you tint, tint the same % all around.
There's no point trying to fool cops that your front windows aren't tinted. They can tell right away. Plus it looks like crap.
I didn't tint my car because I can't tint my front windows. However, I may tint them because in Philly, cops don't care. I see people drive around with 5% tint all around. I know a girl in my apt building that has 5% all around....never gets shit for it.
But when I drive back to Jersey.....