I am designing a PCB with a TPS61090 synchronous boost converter. The datasheet recommends a ceramic 2.2uF and a tantalum polarized capacitor on the output of the chip. They discuss calculating the capacitance of the polarized capacitor and the influence of the ESR on it. But they don't actually mention the voltage rating of that capacitor, and neither do the articles I found when googling. I am planning to output 5.2V on the output (to allow a small voltage drop due to downstream components) so the capacitor should be at least that. But I also read that you need to size your capacitors to double the max voltage, because the capacitance drops with voltage. So what voltage rating would people recommend for the tantalum capacitor? Would 6.3V be enough? Tantalum caps higher than 6.3V seem to get expensive quickly.
Secondly, adafruit makes a board that uses this chip and although their schematic says it's a polarized capacitor, it looks more like a large ceramic capacitor to me. Why would you prefer a ceramic capacitor over a tantalum capacitor or vice-versa for this application?