most states have different tinting laws, some of them like Florida allow tinting all over (except windshield), some others like New Jersey allow tinting only rears (no limits) and no tint on fronts. for instance New York allows 70% on fronts and rears with exception of rear windshield (no limits). tinting the whole front windshield is illegal everywhere, almost in every country.
don't forget that toyota's factory glass comes "pre-tinted" (70-80% VLT), it's not really a tint, rather a natural VLT of glass they use.
examples:
http://www.tintcenter.com/laws/NJ/
http://www.tintcenter.com/laws/NY/
http://www.tintcenter.com/laws/FL/
you should comply with your home state tinting laws as you may be ticketed in any state (not only home state) for having illegal tints according to your home state laws. some cops measure VLT fo your tint and compare with a sticker info.
EDIT:
this link is actually better to compare state vs state numbers. works for US. not sure if all info is valid.
http://www.tintlaws.com/