The usage of
destination tags in the United States on the OSM database is currently nearly equal to
exit_to tags. Here is a graph of the evolution from January 2013 to September 2015.
You can read more about this on the wiki article: http://wiki.openstreetmap.org/wiki/Key:exit_to#Coverage_in_the_United_States
EDIT: I originally used this Overpass Turbo query to create the graph: http://overpass-turbo.eu/s/btc using the dev overpass server, as the normal one was issuing weird errors. However the dev server is not reliable for older data (as pointed out by mmd). I was able to use the normal server again and return correct older data by using simpler queries: http://overpass-turbo.eu/s/by9, http://overpass-turbo.eu/s/bya, http://overpass-turbo.eu/s/byb