I ma trying to find a way to round correctly. So far I get unexpected results for some values.

This is working as designed, though admittedly the cause of the unexpected results is non-obvious.

In Python 2, there's no way to implement `round` for a general type:  instead, the `round` function converts its *input* to a Python (binary) float, and then rounds the resulting value.  So you're effectively doing:

>>> from decimal import Decimal
>>> round(float(Decimal('167.75')), 1)
167.8
>>> round(float(Decimal('167.85')), 1)
167.8
>>> round(float(Decimal('167.95')), 1)
167.9

And the results above are explainable in terms of rounding the corresponding floating-point value:  the closest exactly representable binary float to 167.85 is 167.849999999999994315658113919198513031005859375, which is a touch less than the halfway mark, so rounds down.  Similarly, the closest exactly representable float to 167.95 is 167.94999999999998863131622783839702606201171875, which again rounds down.  167.75 is already exactly representable as a float, so there you get the expected result.

In Python 3, `round` rounds the Decimal object directly without converting to float first, so you shouldn't see the above problems.  In Python 2, you'll need to stick to your quantize approach.

There may be an opportunity for a documentation improvement here: it would be helpful if the Python 2.7 documentation for the "round" function explained that its input is converted to float.

FWIW, the FAQ in the decimal docs shows how to round Decimal objects using the quantize() method:  https://docs.python.org/2.7/library/decimal.html#decimal-faq

Unfortunately, only it Python 3 does the one-obvious-way-to-do-it work.

I'm not sure if this is related or not, but on 3.4.1 I get the following: 

>>> print(round(float(3/2)))
2 (as expected)
>>> print(round(float(5/2)))
2 (expected 3, as float should round .5 up)

Robert:

That is not related. Python 3's round() function, as documented, rounds halves to the even choice; what you describe is the expected behavior.

Python 2.7 is no longer supported.