You can't hide any transaction. But you have a few easy options…
If you truly never want to see them again, you can delete the transactions.
But most people want a just-in-case-I-need-it record of a voided transaction (which I recommend). So:
Now the transaction has zero dollar value and it's reconciled, so you'll never see it in another reconciliation, and it will fade into history in your register. 😀