How can I teach my cat to cover her scat?

My cat uses a litter box and she has never urinated or defecated outside of it. However, she doesn't cover her scat. Instead, she'll just scratch the walls of the litter box (for at least five minutes), or paw at the litter and move it around a little. I adopted her from a shelter where she was brought in at a month old, without a mother, and from what I've read, kittens learn from their mothers how to cover their scat. My conclusion at this point is that she never got a chance to learn how to do that, so I would like to teach her. I know, it sounds weird, but sometimes she can really stink up the house after a really big poop, and it would just make life a little easier (and less smelly) if she could learn that. It's really awkward when I have friends over or I'm having a party, and the cat goes and takes a dump without properly covering it.