You can hold onto the percentage as decimal (value \ total) and then when you want to render to a human you can make use of Habeeb's answer or using string interpolation you could have something even cleaner:
var displayPercentage = $"{(decimal)value / total:P}";
or
//Calculate percentage earlier in code
decimal percentage = (decimal)value / total;
...
//Now render percentage
var displayPercentage = $"{percentage:P}";