Grilled Hawaiian Chicken

4 4-oz boneless chicken breasts, skin on
1/2 cup cooking sherry
1/2 cup pineapple juice
1 teaspoon brown sugar
1/4 cup soy sauce
8 large fresh pineapple slices

Place chicken in a glass bowl; set aside. In a separate bowl, combine cooking sherry, pineapple juice, brown sugar and soy sauce, mix well. Pour over chicken and let marinate in the refrigerator overnight or up to 48 hours. Grill over medium heat until cooked through, remove skin before serving. Grill fresh pineapple slices for garnish.