When Poland first introduced the capital gains tax in 2002, banks were quick to notice the tax law still generally required tax amounts to be rounded to nearest full złoty
when accrued, so they started offering financial products with
daily capitalization, which were effectively exempt from the new capital gains tax, as for most customers, the daily gain would be low enough that the tax on it always rounded down to zero. This only got corrected 10 years later.
I find it fascinating that we could have a whole class of financial products hinging on something seemingly so trivial as a rounding strategy.