As a cloud based POS software, the security is very important. If business looses important datas like customer, payment details, product information it will be a disaster. I would like to suggest optional OTP (sms) verification, Google recapcha in the sign in page (for both admin and cashier). Admin can enable or disable this feature in admin section. As soon as a cashier loged in the account, admin get notfication in the admin panel.
OTP and captcha for login screen