On current master (ca42f2b9a), Ubuntu Intrepid (with libmpfr build from the Jaunty package to get 2.4):
$ cat >rounding.dat <<EOF
2009/01/01 Sample
assets 134.123 FOO @ $8.88
assets 100 BAR @ $8.88
equity
EOF
$ ./ledger -f rounding.dat print
2009/01/01 Sample
assets 134.123 FOO @ $8.8799999999999999975
assets 100 BAR @ $8.88
equity
-bcd
