Please check the rest of the dimes in your pocket, and for that matter, any other denominations. ALL current circulating U.S. coins have the tails side oriented upside-down from the heads side. This has been the practice for well over a century and a half. The orientation is not an error and is nothing special. However, the bubble is potentially an error. It could be caused by a number of things, most likely a place where a bit of gas was trapped during the cladding process and the layers did not stick together properly. It's fairly common problem so there's very little if any extra value attached.