Configuration for minimum charge please

hi , i have a question about making a minimum amount of cash for the receipt to be paid
for example :

lets say that in some days i will make every single order must pay 50 even if he order less that 50

someone order 1 cup of tea = 10 only.
i want him to pay the least of today charge ( thats equal 50 )
and can it be shown like abutton somehow in the payment screen

i am very beginner at sambapos . known that i dont use other than cash payments method and i dont use customer also
is there is away to do that ?

Thank you in advance
I really appreciate any kind of help