There is no built-in functionality to support backup to tape (and hasn't been starting with Windows Server 2008). You'll need to look at third-party software (of which there are plenty of commercial and some free/open source offerings) for that functionality.
NTBackup writes ".BKF" files, which are file-based representations of the Microsoft Tape Format. I know that Symantec Backup Exec has, historically, supported creating tapes in Microsoft Tape Format but, given that you won't be restoring the backups with NTBackup (seeing as how there isn't a Windows Server 2012 version of NTBackup) I'm not sure that Microsoft Tape Format compatibility is really all that important.