It's true, "bankings" is not a word, but that doesn't mean it won't be one someday. Most people in the USA can't write an error free sentence anyhow. Furthermore, the Internet is hardly known for correct grammer. In fact, I'd say the Internet loves to screw up grammer and make non-phrases and slang into real words.
With just doing a simple Google search with no effort, I found that both the Columbia Encyclopedia and thefreedictionary.com both have "bankings" listed. Also phrases like "Net Bankings" and "Internet Bankings" can be found. The non-word also appears 429,000 in web articles as list by Google, so a lot of people are writing it wrongly.
Nevertheless, I think all the above posts are true. It's an okay name (I've seen a lot worse), but it isn't that great either.