I’m writing and mapping from Taiwan, and there are a great number of Taoist temples here. Under the “place of worship” tag, there is no Taoism tag. In future someone at OSM should consider adding this option to the tag details.
You can add the tag religion=taoist to specify that is is a Taoist temple.
It seems this isn’t available as an option in the Potlatch 2 presets, but you can still add the tag. Click on the button for “Advanced” at the bottom of the edit section, then double click in the column for “Key”. Type in religion for the key and taoist for the value.
To get a feeling whether this or any other tag is in use already I recommend to play around with http://taginfo.openstreetmap.org
enter any key or value like religion, confession or taoist and look for the use especially in values.