How to change the shape

I’m knitting a straight sided bag with a flat rectangle bottom and I want to round the sides a bit as I go up. I’ve never knitted a rounded bag (can’t find a pattern I like) but I’m thinking the increasing and shaping shouldn’t be too hard. Should I just place the increases only on the side area or should I increase evenly all around? And is the kfb increase ok or would another be better? There are 42 stitches on circular needles when I start knitting the body of the bag. It’s a small bag, bulky yarn, and I’m knitting bottom up. Any help would be greatly appreciated!

I saved a pattern that had a bottom with rounded corners http://www.ravelry.com/patterns/library/byob-20---bring-your-own-bags-v20 Wyndlestraw Designs © MOIRA that might work for your bag bottom. You do not have to follow the pattern for the sides you can go to another pattern or create your own sides. My personal choice would be to increase with a kfb to have less chance of a hole. Get back to me if the size needs adjusting.
I found another style SHOPPING TOTE OR NEEDLEWORK TOTE http://frugalhaus.com/shopping-tote-or-needlework-bag-knit-epattern/.