There are many companies that sell discounted USPS postage. I saw someone mentioned ShipStation in a reply to your question but check out Pirate Ship too. Make sure you read their articles on the subject of USPS Priority Mail Cubic Rates. It can be a big money saver. Regardless of which posage seller you pick, they all offer pretty much the same deal. I've been using Pirate Ship. When you enter the dimensions and weight of your final packed items, they will show you all the rates available. Sometimes, 1st Class Mail will be the cheapest but offers the same delivery time frame as Priority Mail. Whatever you do, NEVER buy your postage directly from the Post Office either online or at their counter. You will always pay the highest price there and that may drive your customers away.
