Paying for shipping as I go

[gillym82]

I am a very small business and I don't want to rack up shipping charges throughout the entire month and end with a large bill at the end of the month. How can I pay for shipping daily or weekly instead of at the end of my billing cycle? I should add without using an external app. I already use pirateship but them I'm going back and forth and would love to just do everything in one app.