2011-02-23   Rocket Fuel
    Expenses:Travel   $100000000.00 ; trip: Moon 
    Asset:NASA

2011-02-23   Liquid Oxygen
    Expenses:Travel  $232233223.00  ; trip: Moon
    Asset:NASA

$ hledger -f- check

#test bal --group-by "tag('trip')"
#Moon
#       $332233223.00  Expenses:Travel
#end test
#