Even electric (sampled) pianos are tuned that way. The difference from the well-tempered tuning is given by the Railsback Curve (https://en.wikipedia.org/wiki/P

Even electric (sampled) pianos are tuned that way. The difference from the well-tempered tuning is given by the Railsback Curve (https://en.wikipedia.org/wiki/Piano_acoustics#The_Railsback_curve https://en.wikipedia.org/wiki/Piano_acoustics#The_Railsback_...). For the highest and lowest notes it is as much as 30 cent. It comes from the inharmonicity of the strings.