In yesterday’s game BLR–FIN, at 59:16 with Belarus trailing 0–1, Belarussian player injured a Finnish player with a high stick, and received double minor penalty (2+2) for that. However, during the same game interruption, a Finnish player received a minor penalty for roughing (because he avenged the injury). (See the official game summary sheet.)
There are differences between international and NHL hockey, but I believe in this case both would do the same thing: a new 4 on 4 situation is only created when there are an equal number of minor offsetting penalties to both teams.
When there is an uneven amount of minors, then the officials will give the team with one fewer penalty a power-play that is 5 on 4.
There are much more complex scenarios with major penalties and with the two teams having a difference of more than one penalty. The general rule is to negate as many penalties as possible before deciding who has a power-play.