I doubt whether there is a single English term for this (in fact, there isn't one in German: "Anteilsglättung" is not quite correct, since it's the capital - rather than individual shares - that needs smoothing).

These adjustments of capital (e.g. of a company's issued share capital) frequently occurred as a result of converting the capital from, say, deutschmarks to euros. Consider a plc with a capital of DEM 10 million, divided into 2 million unit shares. Converting this into euros would result in EUR 5,112,918.81, or effectively EUR 2.55646 per share. Many companies therefore adjusted their capital to avoid these fractional amounts.