Taking I94 from Minneapolis to I39 down to I74 to I57 you only have two tolls on I39-90 from the Wisconsin Illinois state line to Rockford. With this route you avoid Chicago traffic and many tolls $'s. I wouldn't bother with an IPASS unless you plan on many eastern trips. After 30 years in Chicago Western suburbs I57 was our preferred route South to Florida. Less traffic than I65 avoid Indianapolis and Louisville.
Another option which would avoid tolls would be I35 south to US18 to US218 down I380 to I80 to I74 to I57 no tolls till you reach Florida.