If a T10 has rounded out though, the bolt must be pretty damn tight (or siezed), therefore a screwdriver isn't gonna get the bolt out.
If you drill the head off, this will release the pressure on the threads, and whatever is left you can get out with a pair of pliers (or by hand).
Using a hacksaw won't really help, and it's almost impossible not to nick the top cap with the blade in the process.