Tarr hit a 3-pointer with 1:10 remaining to give Tech its largest lead of the game, 74-53.
Wisconsin (17-9) was led by Tamara Moore, who scored 16. Kyle Black added 14, Emily Ashbaugh 12 and Jessie Stomski had 10 points and 12 rebounds.
The Badgers were up 11-4 on a 3-pointer by Black, but Tech went on a 14-2 run to take a 18-13 lead.
Wisconsin took a 20-18 lead before the Lady Raiders ran off 11 straight points for a 29-20 edge as Wisconsin went 7 minutes and 10 possessions without scoring.
Black scored six straight points to pull the Badgers within three at 29-26, but Tanisha Ellison and Candi White scored to give Tech a 33-26 halftime lead.