Yes you can. Just follow these simple steps:

1. Open the Clock app on your iOS device and tap the Timer tab at the bottom right of your screen.
2. Change the When Timer Ends option to Stop Playing (at the bottom of the list).
3. Set the timer for when you want the SiriusXM app to stop playing, and then tap the Start button.

That's all there is to it. Your iOS device will stop playing audio from the SiriusXM app at the time you have scheduled.