How to check the integrity of a downloaded MacOS X installer?
From Apple KB: Mac OS X: How to verify a SHA-1 digest
[emphasis mine]


  Learn how to verify a SHA-1 digest (also known as a checksum).  
  
  Important: Verifying the SHA-1 of a software update is optional; it is
  provided on Apple software updates for those individuals who want to
  verify the authenticity of an update.
  
  Note: For updates delivered by Automatic Software Update, SHA-1 digest verification is performed automatically for you.
  
  To verify a manually-downloaded software update from Apple Downloads,
  which contains a SHA-1 digest, perform the following steps:
  
  
  Open Terminal (located in /Applications/Utilities).
  Type the following at the Terminal prompt:   openssl sha1 [full path to file]
  


Which would appear to conclude that Apple doesn't maintain a public list of checksums for App Store versions.
However, there is an independent list maintained at https://github.com/drduh/macOS-Security-and-Privacy-Guide/blob/master/InstallESD_Hashes.csv for just the InstallESD components themselves.