"In God We Trust" was adopted by Congress as the official national motto. So it seems futile to argue about taking it off our currency without fighting the more basic argument about its status as a national motto. Personally, I don't really care one way or the other.
The Ten Commandments are another matter. The first four are specific religious beliefs that not everyone agrees with, including the native Americans who were here first. In fact, even the various sects of Christianity don't agree about what they mean. Wars have actually been fought over what a "graven image" is, and Christians can't even agree among themselves about what day the Sabbath is.
Most people who want to post the Ten Commandments are hillbilly redneck Baptist bigots who want to impose their religious opinions on everyone else.