transactions.stream()
                 .filter(t -> t.getType() == Transaction.GROCERY)
                 .sorted(comparing(Transaction::getValue).reversed())
                 .map(Transaction::getId)
                 .collect(toList());

Yes it requires learning several new concepts, but in the end it pays off.

BTW I wouldn't switch old code to this style, because there never seems to be time for that. But new code written like that is perfectly OK IMHO.

EDIT: I really should've checked the code more carefully - the initial version had no indexing variables. Still, it reads better and has less boilerplate.