If you're using iCloud Keychain in order to store your passwords, you can also use it to store your credit card information and sync it across all your iPhone, iPads, and Macs. Any time you pay with a credit card on your Mac, iCloud Keychain will offer to save it. However, you can also add a card manually any time it's convenient. That can save you a mad dash to your wallet in the middle of the night.
That's all there is to it. iCloud Keychain will then sync your card information between all your OS X Mavericks and iOS 7 devices.
If you have specific questions about iOS 7 or OS X Mavericks in general, check out our iOS 7 help and discussion forum or OS X Mavericks help and discussion forum. For more on Safari in specific, check out our ultimate guide: