In a large skillet, cook beef, onion and garlic over medium heat 6-8 minutes or until beef is no longer pink, breaking beef into crumbles; drain., Transfer beef mixture to a 5-qt. slow cooker. Drain 1 can of tomatoes, discarding liquid; add to slow cooker. Stir in beans, chili powder, cumin, salt and remaining tomatoes. Cook, covered, on low 6-8 hours to allow flavors to blend., Mash beans to desired consistency. Serve with toppings as desired.