SSL with no password enconding

Question

I'm new in security matters. I have been ask to work with Unnax Payment API, for make transactions, but when I checked the API, I saw that they send the username and password without any kind of encriptation, just plain text. (https://www.unnax.com/sandbox) - GoTo -tryout- tab. We wrote them, and they said that they use SSL and https, so, it's not necesary to encript the information. But I have seen other banks which do the same using ssl and https and they DO encryptation. My question is, if is secure enough to send my client 's banks account using the Unnax API?? Thanks