What would happen to penny stocks? If they round up to the next 5 cents that's up to a 400% increase and would make their holders millionaires overnight...
Don't worry, here over in Europe we have several countries that have no 1/100 splitting of their currency since dozens of years, because the smaller coins have vanished after some inflation.
The prices will remain as they are today (accurate to one penny), but on checkout the amount will be rounded.
Let's say you buy
1 item at 0,99 = 0,99 ==> You pay 1,00
2 items at 0,99 = 1,98 ==> You pay 2,00
3 items at 0,99 = 2,97 ==> You pay 2,95
4 items at 0,99 = 3,96 ==> You pay 3,95
5 items at 0,99 = 4,95 ==> You pay 4,95
If the smallest fraction of local currency is 0,05, then prices below 0,05 in local currency at checkout make no sense and are avoided, so perhaps for penny stocks at a share price of 0,01 there would be a minimum order of 5, 10 or 100, I suppose.