Depends. Some mints/gum don't smell that good, just taste good. TicTac makes this 'Cherry Passion' flavor, and it tastes alright, but really isn't pleasant on the breath...
What I do is take a piece of gum and split it in half. Seeing as a whole gum and a half gum have the same "life", go with half a gum. It does the same trick.
Though, if you've been eating garlic, onions, and the sort, then a whole piece would be better.
You might be better off just brushing more often though!