For future reference: Closed scissors will cut the tape on a box. So will a ballpoint pen. That's what our produce manager uses. Jab the pen through the tape and pull. She opens dozens of boxes that way every day and the pen still works. Easier on the fingers.

If nothing in the box is breakable and the contents doesn't quite fill it up, just punch the top. The cardboard will move, but the tape won't. Then just pull the tape off.