Write a function to round the given number to the nearest multiple of a specific number.
def round_num(n,m):
    a = (n //m) * m
    b = a + m
    return (b if n - a > b - n else a)
<s>[INST]<<SYS>>Given a task and its code, generate test cases for the code.<</SYS>>Write a function to round the given number to the nearest multiple of a specific number.
def round_num(n,m):
    a = (n //m) * m
    b = a + m
    return (b if n - a > b - n else a)[/INST]assert round_num(4722,10)==4720
assert round_num(1111,5)==1110
assert round_num(219,2)==218</s>