To take cash payments you simply need to enter the total amount of cash given in the amount charged field, and then select cash.
Note: For calculating cash tendered amounts greater than the total of the sale you'll need to enable the Change Calculator.
The Change Calculator gives you the option to calculate how much change you have to return to a client when they pay with cash.
To enable the feature, go to: Settings > Payments & Checkout > Advanced Settings
On the checkout payments screen, select the Cash button.
Enter the amount received. The change will automatically be calculated for you.
Once confirmed, the sale will be completed and closed.
If you are using the Cash Drawer feature, it will also be updated automatically.
For more information on the Cash Drawer feature please go to: Cash Drawer