> Like having to declare a constant for the number of cents in a euro/dollar.

I agree with your point, but this is a bad example. Naming these constant CentsInEuro and CentsInUSDollar is consistent with the style guide.

As silly these examples are in isolation (of course a cent is 1/100 of a euro or a dollar), if you are writing code that processes currencies beyond euro and dollars, you will quickly end up with (using Chinese Yuan as an example):

    const (
        JiaoInCNYuan = 10
        FenInCNYuan = 100
        ...
    )

At which point adding

    const (
        CentsInUSDollar = 100
        CentsInEuro = 100
        ...
    )

is not just reasonable but a good idea.

Additionally, suppose your code needs to deal with historical currencies, you'll most likely need:

    const (
        ShillingsInOldBritishPound = 20
        PenceInOldBritishShilling = 12
        ...
    )

This is also a good example that the knowledge that a cent is 1/100 of a dollar or euro is highly culture-dependent. A British programmer from as late as 1970 will tell you that it's silly to create constants for these: of course there are 20 shillings in a pound and 12 pence in a shilling, everyone knows that! (I also like to think that they'd assume that a "cent" is 100 dollars because that's what centum means in Latin, but it's probably highly unlikely for them to never know US dollars and cents.)