Unfortunately I live in Sheffield but rarely go in?
Found this website that might be of use? But there to many variables hope it helps?
Usually better off parking just out of town there’s some side streets just off London rd that are cheap or free at certain times but no good if your over the other side of the city, I think John Lewis do a deal if you buy something then parking in there car park is cheap, possibly have a cuppa? https://en.parkopedia.co.uk/parking/sheffield/?arriving=201901041730&leaving=201901041930