How is their coins like? I mean their denomination.
Imagine paying 177500 with 1ruppiah coin...

Their coins are almost totally worthless, and are rarely
used.
I only had three coins of 100 rupiah each, and I never used
them. And I really meant 'worthless', because 1 SGD = 7800
rupiah.
Over there, 'small change' means 1000, 2000, and 5000 rupiah
banknotes, which are all still less than 1 SGD anyway.
Complicating matters is the way they casually tell you the
prices. The salesgirl may say things like 'empat lima'..... which
is literally 'four five'. The problem is that that could mean
either 45 000 or 4 500, and I would get frustrated having to ask
'hundreds or thousands?'