An unverified backup is not a backup.
I have seen cases (using tar and cpio) where users changed tapes every night and did a check every morning to confirm the backup ran. When the hard disk failed, the tapes were found totally unreadable (even by a recovery house) because the tape velocity of the drive was unsteady.
We have used bru quite successfully. and it's not expensive if you don't mind a little "license bending" by using the "personal" version for business use. I've been involved with sites using Lone Tar, but having to call for a new license code at 2:30 am so you can restore to a new drive is a bit of a drag, even if you can find the paperwork.
In cases of extreme cheapness I have used tar -c followed by then a tar -t with any error messages written off to a text file checked by the user in the morning. At least that confirms the tape is readable.