When the DR sends an update, the destination multicast address is 224.0.0.5
Actually, this is also better to memorize, the OSPF are bigger than the big ones, so the address of the bigger ones is on behalf of the DR/BDR, which can be interpreted as the address 224.0.0.6 assigned to the DR/BDR. BDR allocated 224.0.0.6 this address, want to communicate with it when sent to this address.