The Front Register is where you sell goods and services, take deposits for Work Orders, return and exchange goods. One user at a time can be working in a register. To release the register you are working in simply log off from the Action Menu.
New Registers can be created in Store Operations >> System Manage >> Registers.
When you close a register you can count your cash drawer then or use Quick Close and count it later. Count it later in Sales >> Manage Cash Register Batches.
All sales default to Walk In Customer as the selected customer. You can create or select a different customer any time during the sale until you attach a customer related item like a store credit as payment or Work Order deposit.