An 85-year-old nun was robbed of her cash Friday afternoon at a church in the Mission Hill section of Roxbury, Boston police said. The woman was standing at the window of the rectory office at the Basilica of Our Lady of Perpetual Help on Tremont Street, when a man took the small amount of money that was placed on a counter, police said. Officers searched the area for the suspect, who was described as being in his late 30s, with a slim build and dark hair and wearing a leather jacket. Police had made no arrests by Friday night, and the sister was not injured.