Both .tar and .cab files are compressed archives, so it should be possible to repack one to another should you really need it. However, when you convert the archives, you won't be able to use for their original installation purposes.
Convert Unix standard Archive format, Tape Archive to Windows Cabinet Compressed Archive.
We have found 3 software records in our database eligible for .tar to .cab file format conversion.
Microsoft Windows software - convert tar to cab on Windows
Freeware file compression tool
Convert from tar file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned tar to cab. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
One of the many available file compression utilities
A freeware archive utility that supports many archive formats