all statements in postgresql are self contained transactions, and you cannot
change that.
To answer your question directly, you don't have to, it will all be a
transaction.
The best example of that is to run following query in psql:
CREATE TEMP TABLE foo() ON COMMIT DROP;
the table will not exists anymore after running it. Precisely because it was
'automatically' wrapped in begin/commit, and dropped at the end of it.
hth