Can the metal tab at top of a TO-220 package be cut off?
I have done it, but I would never ship anything like that out.

I suggest clamping the "waste" end of the TO-220 in a vise firmly and sawing it with a fine tooth hacksaw blade, not allowing anything to touch the epoxy. 

Shearing would be much faster and neater, but I fear it would distort the metal and cause the part to become more unreliable than necessary.