The trailing digits You don't want to appear are normal behavior with floating point numbers (specifically with single precision ones like "float" or "Single") due to their intrinsic rounding that lead them to store the value in an approximated form.
To avoid that akward representation, explicit rounding is needed.
To accomplish that, if You are using a DataGridViewTextBoxColumn then You have to replace DefaultCellStyle
property or its Format
Column1.DefaultCellStyle.Format = "N2";
You can change format directly from code or through the grid designer.