Java and Python, for a start, have decimal number types in their standard distributions.
In Python, the story looks slightly better:
from decimal import *
>>> getcontext().prec = 6
>>> Decimal(1) / Decimal(7)
Decimal('0.142857')
But I think it's important to make sure programmers don't end up with the idea that they might as well store money amounts in binary floating point because the language they are using doesn't support decimal.
.getcontext().prec = 6
AFAIK (and I don't do this for work), after every calculation you manually need to call quantize as in
cents = decimal.Decimal('.01')
money = price.quantize(cents, decimal.ROUND_HALF_UP)https://en.wikipedia.org/wiki/Decimal_data_type
Also, I don't try to endorse the Python API. I don't even use it. I just pointed out their api is easier since the operators work with their decimal data type, as opposed to the Java version.
In general you need to know when to round and to how many digits. But my complaint was that languages have a natural API for binary floating point, which is useful for scientific number crunching, but rarely anything comparable for commercial calculations.
I have not tried to design a natural API for fixed (but parameterizable) decimal precision and the implicit rounding required. But I would be surprised if it's impossible to come up with anything less verbose (explicit constructors everywhere) and less error prone (forgetting to call rounding).
If you're on the JVM, Groovy is nicer in that regard. It uses by default BigDecimal and BigInteger for literal numeric types, and has operator overloading: http://groovy-lang.org/syntax.html
Apache Groovy uses by default BigDecimal for literal decimal types, but only uses BigInteger for literal integral types when it would overflow the largest available primitive type for that literal. You can force a BigInteger by using the suffix `g` on the integral literal. Perhaps misunderstanding this is the source of some hard-to-find bugs in some of your Groovy code.