Is there a way to see battery percentage on an iPod touch 5g running iOS 8?

Yes by using a third party app. There are lots of them, mostly free. Do a search in the app store.

Also try:

http://modmyi.com/forums/ipod-themes/816715-add-battery-percentage-ipod-touch-5t h-generation-ios-6-without-jailbreaking.html

Not that % battery on an iPod is not accurate. You will see large fluctuations in % battery with load changes like turning iPod off and then back on, That is normal and expected.