pprint with custom float formats

I have a nested dictionary structure with tuple keys. Here's what an entry looks like when I pretty-print the dictionary using pprint:

...
 ('A', 'B'): {'C': 0.14285714285714285,
              'D': 0.14285714285714285,
              'E': 0.14285714285714285,
              'F': 0.14285714285714285,
              'G': 0.14285714285714285,
              'H': 0.14285714285714285,
              'I': 0.14285714285714285},
...

It's pretty nifty, but I'd like to customize it further by cutting down some extra digits from the floats. I was thinking that it'd be possible to achieve by subclassing pprint.PrettyPrint but I don't know how that would be done.

Thanks.