Transaction Rollback errors

when my application (Node.js) receives a class 40 error:

Class 40 — Transaction Rollback
40000	transaction_rollback
40002	transaction_integrity_constraint_violation
40001	serialization_failure
40003	statement_completion_unknown
40P01	deadlock_detected

then does it mean PG has already rolled back the tx and therefore I should not attempt to roll it back again? Thanks,

S.