how to index a numeric(12,2) column?

I'd like to create an index on a column whose type is NUMERIC(12,2).
There appears to be no default operator class for the numeric type.  What
class should I use instead?  My guess is that something like this might
work:

CREATE INDEX foo_idx on foo (bar int8_ops);

Will that work properly?  Will it do me any good?  Is there a better way?