code: @Override
      public RoundedMoney multiply(Number multiplicand) {
          BigDecimal bd = MoneyUtils.getBigDecimal(multiplicand);
          if (isOne(bd)) {
              return this;
          }
          BigDecimal dec = number.multiply(bd, Optional.ofNullable(
                  monetaryContext.get(MathContext.class)).orElse(MathContext.DECIMAL64));
          return new RoundedMoney(dec, currency, rounding).with(rounding);
      }
docs: /*
  (non-Javadoc)
  @see javax.money.MonetaryAmount#multiply(Number)