Many manufacturers do not allow this with all volume streams and many other applications will only let you set one at a time. True Silence is the only one tap solution to the problem! It also remembers and restores your previous volume levels on a second tap.
True Silence is lightweight, open source, and requires no permissions to run. It is also ad free! Please see the website if you would like to give feedback or contribute in any way.
Other programs can always 'unsilence' you. This version has a setting that will allow True Silence to check and re-silence the device periodically.
*This version is not compatible with versions of android older than 3 (Honeycomb). There is another version that will support older devices: https://play.google.com/store/apps/details?id=com.panic