"...retailers will be rounding their price up to 10c."
This was a common argument when first 1c, then 2c coins were ditched.
It hasn't seemed to work that way; even today many prices have a 1c, 2c, 3c, 4c last digit which is rounded up or down in the total spent.
This could work if we give up the 5c coin, too. The final amount would be rounded up from 5c or down from 4c.
