Round a number to 5 cents up in java

Question

I'm trying to figure out how to round a monetary using this Rules:

 Tax calculated | Taxe imputed |
|---------------|--------------|
|          0.99 |         1.00 |
|          1.00 |         1.00 |
|          1.01 |         1.05 |
|          1.02 |         1.05 |

I tried various methods for rounding but always I get an error:

I have 2 books at 12.49€ with tax 10%; and one cd at 14.99€ with tax 20%

I tryied this method but always get false result

double number = 12.49 * 0.1 * 2;
double number2 = 14.99 * 0.2;
double round1 = Math.round(number * 100.0 /5.0) * 5.0 / 100.0;
double round2 = Math.round(number2 * 100.0 /5.0) * 5.0 / 100.0;

the console print 5.5 (round1+round2) but I should get 5.53

Help Please

Answer 1

1. (double)Math.round(value * 100000d) / 100000d

   That's for 5 digits precision. The number of zeros indicate the number of decimals.

   please take a look at this (stack-overflow question) and this (oracle documentation)

    double round1 = Math.round(number * 100.0 /5.0) * 5.0 / 100.0; double round2 = Math.round(number2 * 100.0 /5.0) * 5.0 / 100.0;

   so , either you should reconsider the position of parenthesis (re-arrange the values) or please use another variable without round first and then do the round() operation.

   in this case simply,

    double round1 = Math.round(number * 1000.0 /5.0) * 5.0 / 1000.0; double round2 = Math.round(number2 * 1000.0 /5.0) * 5.0 / 1000.0;

   might solve the problem , but it is better to do it properly , so that it will remain meaningful later.

2. Using Decimal format for string output , eg.,

    double val=8.888888; DecimalFormat df = new DecimalFormat("#.###");//for 3 decimal places df.setRoundingMode(RoundingMode.CEILING); String value=df.format(val);

   for more info check Class DecimalFormat , remember that it can be parsed to number , iff it is really necessary.