One IC as Step up and down converter

Please look at the TPIC74100-Q1, which is a Buck-Boost that generates 2 fixed 5V output rails (VOUT and 5Vg). It is a buck-boost (step-up and step-down converter) with a VIN range from 1.5-40V

If you need to generate a voltage other than 5V, I suggest you look at the TPS63000-Q1. This part is also a buck-boost but the output voltage can be set by a resistor divider into the feedback (FB) pin. This device only has one output rail, but you can use 2x of them to generate 2 output rails.