The iPod touch 5 is the last A5 device that cannot be untethered downgraded to iOS 6. If retro iOS 6 is your goal, sell the iPod touch 5 and buy an iPhone 4s or iPad 2 (which can downgrade untethered using OTA blobs).
No, you cannot perform a standard, untethered downgrade to iOS 6 on an iPod touch 5th generation. downgrade ipod touch 5 to ios 6