Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$55.85	12.833%	$63.0172	$63.02	$63.00	$63.00
Purchase #2	$29.78	13.339%	$33.7524	$33.75	$33.75	$33.80
Purchase #3	$9.52	6.437%	$10.1328	$10.13	$10.15	$10.10
Purchase #4	$248.56	10.663%	$275.064	$275.06	$275.05	$275.10
Purchase #5	$244.37	8.775%	$265.8135	$265.81	$265.80	$265.80
Purchase #6	$246.37	13.767%	$280.2878	$280.29	$280.30	$280.30
Purchase #7	$124.68	6.870%	$133.2455	$133.25	$133.25	$133.20
7 purchase totals =	$959.13		$1,061.3132	$1,061.31	$1,061.30	$1,061.30