Some apps do close by swiping the recents tile, some don't.
I won't use the force close option in the app info screen, it's only really for force closing a problem app.
Temporarily install an OS monitor app, check whether after use the app is using CPU and if it's not then don't worry about it because Android will close it when it's ready too.
I'd just come out of the app with the back button, it's as close to a close button as you'll get.