Mike,

The vast majority of programs to send cw via the computer  do not use 
the sound card.   Almost all, including the ones  in logging software, 
hard key the rig via the key jack on the radio.    Using the sound card 
to generate cw is kind of a mickey mouse way to do it, but it can be 
done.   The interface for hard keying cw is a simple 1 transistor, or 
opto isolator, or is part of a multi function interface.   One problem 
with trying sound card cw is that your radio is in ssb mode and your 
filtering is not  what you would have in  cw mode.

What you wind up doing is going to depend on your particular interface. 
  Of course anything that will decode incoming cw will use the sound card.

73 and good luck,
Steve KW3A