Can a percentage be tagged?

The short answer is no, percentages cannot be tagged as percentages are not values and only values are taggable within XBRL.

If you do want to tag a percentage, what you can do is to tag it with an ix:nonFraction element with a unit of pure12 and a scale attribute set to -2. This will result in an XBRL representation of the value correct notation, which means it reads as 0.81 instead of 81%.