What I understand now is that the internal base 2 representation is not likely to cause any problems if I am dealing with only integers.

Yes, as long as they're not too large. If you keep the numbers small than ±9,007,199,254,740,992, you'll be ok.

>perl -e"printf qq{%.0f\n}, 9007199254740992 + 3"
9007199254740996    even? how odd!
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Have fun calculating tax without using decimals, though. What you want to do then is perform rounding:

# If working with cents
$tax_amount = sprintf('%.0f', $amount * $tax_rate);
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