code: public void setRoundingIncrement(BigDecimal newValue) {
          int i = newValue == null ? 0 : newValue.compareTo(BigDecimal.ZERO);
          if (i < 0) {
              throw new IllegalArgumentException("Illegal rounding increment");
          }
          if (i == 0) {
              setInternalRoundingIncrement(null);
          } else {
              setInternalRoundingIncrement(newValue);
          }
          resetActualRounding();
      }
docs: <strong>[icu]</strong> Sets the rounding increment. In the absence of a rounding increment, numbers
  will be rounded to the number of digits displayed.
  
  @param newValue A positive rounding increment, or <code>null</code> or
  <code>BigDecimal(0.0)</code> to use the default rounding increment.
  @throws IllegalArgumentException if <code>newValue</code> is &lt; 0.0
  @see #getRoundingIncrement
  @see #getRoundingMode
  @see #setRoundingMode