SQL Server 2012 Can't log in with machine account
It is most likely not the DOMAIN\computer$ at all. This message is known to be a misleading. I think all it wants is that  "NT AUTHORITY\NETWORK SERVICE" be granted the server access. Open SQL Server login properties and add this account. Also, check what user is used in the IIS to impersonate anonymous user, it should be something like "IUSR_ServerName". Grant access to this user as well