Combining two SELECTs by same filters

Hi,

I've a table like:

=> SELECT dt FROM sales WHERE id = 2;
dt
----------------------------
2005-10-25 21:43:35.870049
2005-10-25 21:43:36.254122
2005-10-25 21:43:36.591196
2005-10-25 21:43:36.893331
2005-10-25 21:43:37.265671
2005-10-25 21:43:37.688186
2005-10-25 22:25:35.213171
2005-10-25 22:25:36.32235
(8 rows)

And I want to collect the count of sales at hour = 21 and hour = 22.
For this purpose, I'm using below SELECT query:

=> SELECT
-> (SELECT count(id) FROM sales
-> WHERE id = 2
-> AND date_trunc('hour', dt) = '2005-10-25 21:00:00'),
-> (SELECT count(id) FROM sales
-> WHERE id = 2
-> AND date_trunc('hour', dt) = '2005-10-25 22:00:00');
?column? | ?column?
----------+----------
6 | 2
(1 row)

Isn't it possible to combine these two SELECTs as one. Because one of
their filters are same: id = 2. I'm just trying to avoid making 2
scans with nearly same filters.

Regards.