Here's what the MSP airport says:

Lockers

Storage lockers are available in secure areas of Terminal 1-Lindbergh. The locker dimensions are approximately 23" tall by 15" wide by 35" deep and can accommodate carry-on-sized luggage. For security purposes, lockers are equipped with fingerprint technology to ensure only those who store the bags can retrieve them. Locker rental costs: $4 for first 4 hours; $8 per day. The lockers are intended for storage of 48 hours or less, and are emptied by Smarte Carte after 48 hours. Lockers are located in the following areas at the Lindbergh Terminal:

near Gate C2
near Gate C13
entrance to Concourse F

http://www.mspairport.com/passenger-services.aspx