The Police Department has received a $10,000 state grant to combat underage drinking, and will be using the money for the next five months to monitor retail stores, bars, and restaurants that sell alcohol. Undercover officers will be assigned to retailers to deter the purchase of alcohol by minors, according to an announcement by the department. Officers will also be conducting compliance checks of businesses licensed to sell alcohol. The money will “substantially increase enforcement” through September, according to police. Newton’s department is among 25 police agencies across the state that received a grant under the program.