Rounding up or down to the nearest 50 cents

I have a price list I need to round up or down to the nearest 50 cents?

I have tried using =IF without much success.

For example:( the price range varies from $1.20 up to $50.00)

4.13

4.27 would round down to 4.00

4.33

4.42 would round up to 4.50

4.68

4.71 would round down to 4.50

4.82

4.92 would round up to 5.00

Many thanks for your help.

Regards

Peter