Help me in solving RETURNCHANGE problem

My issue

okay i am failing on the input
my output is 10
expected output is 90, How?

My code

def amtReturned(x):
    rem = x%10 
    if rem <5:
        amt = 10* (x//10) 
    else : 
        amt = 10 *(x//10) +10

t = int(input())
for i in range(t):
    cost = int(input())

Learning course: Number theory
Problem Link: CodeChef: Practical coding for everyone

u have to print the change u will get after paying 100.
so print 100-amt.
rest of your code is correct.