The finance systems I’m familiar with generally don’t rely on DNS for security and, more commonly, don’t rely on it at all. For systems operating over the open Internet, the most common security mechanisms involve pre-shared key pairs. For systems not on Internet, IP (v4) addresses are generally used directly.

I’m actually generally disappointed that TLS in the context of web browsers essentially only uses the CA system for identification and security. It’s wrong at both ends of the spectrum. There are systems where manual key distribution would be fine, and avoiding the CAs as a weak point would be beneficial. And there are systems where the CA system flat out does not work (e.g. anything where the servers are not connected to the Internet and do not even have every-few-days Internet access). Neither of these use cases are handled well by web browsers. (DNSSEC doesn’t help either, of course.)