Rounding will happen eventually, but it's a slow change. Initially I'd expect everything to be in the old units but labelled metric. As an example, here in New

Rounding will happen eventually, but it's a slow change. Initially I'd expect everything to be in the old units but labelled metric. As an example, here in New Zealand most bars sell beer in 500ml glasses, but the one I go to sells 568 ml glasses. The same happened when I was in the UK and the milk had to be sold in metric quantities. You don't need to force people to change their thinking, but if you start labelling things in metric it will change over the generations.