Wage Garnishment

As a server, my paychecks are $0 as it is all taken out for taxes. I have a garnishment from an old property management company I rented from back in 2015. My employer is trying to take part of my cash tips at the end of the shift in order to satisfy my wage garnishment since my paychecks are not enough to garnish. Is this legal? Do I have to forfeit a percentage of my cash tips?

Thanks in advance for any insights provided ~