Then you should store the time as well, because the number of decimals in a currency can change (see ISK). Also, some systems disagree on the number of decimals

Then you should store the time as well, because the number of decimals in a currency can change (see ISK). Also, some systems disagree on the number of decimals, so be careful. And of course prices can have more decimals. And then you have cryptocurrencies, so make sure you use bigints