Paperless Bill or eBill feature should be available to save paper.
In this case, a link over SMS & E-mail can be sent to customers along with the link for the bill. This should be added as an option to avoid usage of paper bills.
Cashier can ask the customer whether they want a physical bill or not.
Guest
Bill on Whatsapp OR message required by customers also to avoid physical touch
Paperless Bill or eBill feature should be available to save paper.