TD Bank, which has one of the largest financial institution footprints in Maine, will soon close three of its 44 branches here as part of a sweeping cutback across 15 states. According to a filing with the federal Office of the Comptroller of the Currency, the bank will permanently shutter retail banking locations at a Shaw’s supermarket, 600 Center St., Auburn; at 229 Elm St., Biddeford; and at a Hannaford supermarket, 35 Elm St., Brunswick. In a statement emailed Monday to Mainebiz, a TD Bank spokeswoman confirmed the closures and said they are among 81 being made by April 23 throughout TD Bank’s Maine-to-Florida territory. That number represents 7% of its 1,223 branches.