public void Currency_can_round(CurrencyRoundingMethod method, decimal value, decimal result)
{
value.Round(method).ShouldEqual(result);
}
/// <summary>
/// Rounds a currency value
/// </summary>
/// <param name="value">Value to round</param>
/// <param name="method">Currency rounding method</param>
/// <returns>Rounded value</returns>
/// <see cref="https://en.wikipedia.org/wiki/Cash_rounding"/>
public static decimal Round(this decimal value, CurrencyRoundingMethod method)
{
var result = Math.Round(value, 2);
var frac = (result - Math.Truncate(result)) * 10;
if (frac == decimal.Zero)
{
return(result);
}
switch (method)
{
case CurrencyRoundingMethod.Down005:
case CurrencyRoundingMethod.Up005:
frac = (frac - Math.Truncate(frac)) * 10;
if (method == CurrencyRoundingMethod.Down005)
{
frac = frac < 5 ? -1 * frac : 5 - frac;
}
else
{
frac = (frac < 5 ? 5 : 10) - frac;
}
result += frac / 100;
break;
case CurrencyRoundingMethod.Down01:
case CurrencyRoundingMethod.Up01:
frac = (frac - Math.Truncate(frac)) * 10;
if (method == CurrencyRoundingMethod.Down01 && frac == 5)
{
frac = -5;
}
else
{
frac = frac < 5 ? -1 * frac : 10 - frac;
}
result += frac / 100;
break;
case CurrencyRoundingMethod.Interval05:
frac *= 10;
if (frac < 25)
{
frac *= -1;
}
else
{
frac = (frac < 50 || frac < 75 ? 50 : 100) - frac;
}
result += frac / 100;
break;
case CurrencyRoundingMethod.Interval1:
case CurrencyRoundingMethod.Up1:
frac *= 10;
if (method == CurrencyRoundingMethod.Up1 && frac > 0)
{
result = Math.Truncate(result) + 1;
}
else
{
result = frac < 50 ? Math.Truncate(result) : Math.Truncate(result) + 1;
}
break;
}
return(result);
}