See AlkaPoint working
You can look around AlkaPoint before you sign up. The demo uses sample data, so nothing you do there affects a real business.
What to try
Ring up a sale and watch the stock fall. Put part of a sale on credit and then pay some of it back. Add a product and set its price. Open the reports and see the profit the sales produced.
When you are ready
Register your own business, choose the kind of shop you run, and your workspace is created with the categories that fit it. You can be making a real sale within a few minutes.