No, the only way to close them is as I described. You can overtly double click the home button and close an app once you decide "I'm done with this for now.", but clearly that's not what's intended by the designers. The price you would pay is having to wait longer to start the app next time, and forgetting the context that was in place when you last used it.
Generally speaking, mauijiminar is correct ahd open apps don't significantly contribute to battery drain. Things that can really drain your battery are, for example, apps that are open and continuing to use location services. You can see some of these by looking at Settings > Privacy > Location Services and see which ones have little arrows next to them. Probably the biggest power hog would be setting a reminder of the form "Remind me to ... when I leave home."