Making a minor adjustment on vehicle alignment?

Both front tires on my 2005 Sienna are wearing on the outer edge of the tread (like the tires are tilted outward on the top). I can manage my way around basic auto repairs and was wondering if there was an adjustment I could try. It looks like the same amount of wear on both tires. Long ago in my high school auto we were showed how you can adjust the tie rods, etc., the caveat being to mark where you started. I don't see where I could make an adjustment on this vehicle to bring the tires more vertical. does anyone know? I don't have the money to bring it in to a shop, especially since I'll probably try to get sold on a whole front end package. The vehicle runs well, no noticeable pulling or vibration, just extra wear on the outer edges.