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	$84.81	11.366%	$94.4495	$94.45	$94.45	$94.40
Purchase #2	$55.32	10.559%	$61.1612	$61.16	$61.15	$61.20
Purchase #3	$138.86	11.424%	$154.7234	$154.72	$154.70	$154.70
Purchase #4	$92.47	10.631%	$102.3005	$102.30	$102.30	$102.30
Purchase #5	$159.51	7.634%	$171.687	$171.69	$171.70	$171.70
Purchase #6	$206.98	13.762%	$235.4646	$235.46	$235.45	$235.50
Purchase #7	$181.90	10.123%	$200.3137	$200.31	$200.30	$200.30
7 purchase totals =	$919.85		$1,020.0999	$1,020.09	$1,020.05	$1,020.10