I don't do online banking but sometimes I buy stuff with a credit card. I usually use a prepaid credit card so if the credit card number falls into the wrong hands, they won't be able to use the number (since you get a new number every time you top up) but sometimes I order stuff for other people who give me their credit card to do it.
The fact that using a VPN, means all data you send is encrypted would be a plus but is there a risk of people on the VPN intercepting credit card numbers or other confidential data? I haven't yet got my head around how VPNs work but I have a good understanding of how Tor works. I can see that all data is encrypted until it reaches the end node, then its decrypted and sent to the target site. Since the end node can be anyone on the tor network, someone with a sniffer can intercept data. In fact, I read an article about a Swedish hacker who got hundreds of usernames and passwords of US government workers who thought that by using Tor, their data would be completely safe. I don't really know how VPNs work, does the same problem exist where someone on the VPN can sniff data?