That's how many places in the world charge for fares. Flat fares (one price for any journey) were always regarded as a North American phenomena, although they have spread. When I was a kid in Britain the city bus fares went up in 1p increments every half mile ! Remember the city transport systems in Singapore, Hong Kong, etc were planned and managed by Brits for many years, and the double deckers still come from here. Dublin in Ireland is still the same too, all fares requiring at least 4 coins if paid exactly (and no change is given). Singapore Bus really wants you to use the Ez-Link cards you describe, which give a significant discount over cash. At least the cash fares are rounded to 20 cents above.

If you have a flat fare in a large city you either require substantial subsidy for the longer distance riders (with a low fare) or discourage short distance riders (with a high fare) - the US experience.