I'm currently working with pricing data, and so I want all my values to rounded up to the nearest .5 or nearest .9. Likewise, I want to also round all my values down to the nearest .5 or .9 (whichever comes first). For example if I had the values 3.54, 4.57, and 5.31, I would want them to round up to 3.55, 4.59, 5.35 and round down to 3.49, 4.55, and 5.29. What is the best way to go about doing this?