It was common practice with tube type fullwave rectifiers to connect the secondary centre tap to the equipment chassis,& hence to the Mains Earth.
If you,on the other hand,wish to connect the centre tap of the primary to Mains Earth,that is not a good idea.
In the case of a single phase supply with the Neutral & Earth connected together at the building entry point,you are in effect,shorting out one half of your primary,& applying the full Mains potential to the other half.
If you have an earth leakage detector (RCD in Oz speak),that will operate & turn everything off before you can cook your transformer.
if you are using the strange North American split phase 240v system,it may be OK,providing both sides of the centre tapped pole transformer are perfectly balanced.
If not,your RCD will again operate.
It is unnecessary,& probably forbidden by your regulatory authority.