@Monish Koyyot is actually right about conclusion, but his reasoning is false. First thing you need to be aware of: FIFA, nor UEFA for that matter, keep, show or in any way calculate shot percentage(conversion rate) stats - they're not standard in football statistics. Major Football leagues, like Premier, Primera, Bundesliga, Calcio, do often provide more in-depth player stats, but there's no written standar on how's this done.
Another thing, you'll need to understand is what an shot percentage actually is, as in, which stats go into account. So, conversion rate, or shot percentage, in football, is represented as successfulness in scoring a goal against opposition team, not really as one's general contribution to the game. I know that may not seam right, but that's how all major football leagues define it.
Shot percentage is calculated by dividing a total number of shots with total goals scored. Note that if one player is responsible for an own goal, or auto-goal, he/she did not really score. I know it's common phrasing to say that he/she scored own goal, but in football terminology, that doesn't really account for scoring a goal.
That being said, in none of the major Football leagues own goals go into shot percentage calculation. Penalties are, on the other hand, often calculated as 85% of the in game goal score.