Retail is the concept of selling the product to end customers or the actual users, who are using/ consuming the product. So for them the tax is included with the price. Let's say when a product cost 50(in any currency  unit). it has the tax included with price. Where as the bulk buyers doesn't have the tax included with price. It depends on the company as well

This pricing is between business to business. So normally, the price is not included with the product price that we given to customer. and additionally Tax charges will be applied with it. Usually the Whole sellers and Distributors of multi product buys the large quantity of items that makes them to buy it tax excluded with price. While billing the customer, the Tax will be added with the product cost. 

Soon, we are focusing to launch an e-commerce store, which comes with good features. and will keep updating it. The E-commerce pricing is bit different than the other two pricing. Because it depends on the product, most of the time less than the retail pricing. and some times it changes in time to time. So the e-Commerce pricing is different than store and wholesale prices. 

Ofcourse, Its possible to expand the pricing types based on your needs. From TamilAccounting its good to have your own Sales types and custom types. Which also sets the Tax type whether included or excluded along with it. 

The Connects in different ways to a transaction. Because it can be depends on several factors, such as item or service, Customer, supplier, and type of customer and Supplier. And also with Sales type. Based on the sales type we can classifying the Tax inclusive or Exclusive.