Sounds like a zip code database issue.

Many zip codes have multiple city names.  Plug the zip code into the USPS database and see if both names come up:

https://tools.usps.com/zip-code-lookup.htm?citybyzipcode

I'm guessing either the tax software or the IRS database is "correcting" the city name based on automatically picking one name from the list.  See 22102 as a good example of one zip code with four names.

Rick