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	$85.39	4.359%	$89.1122	$89.11	$89.10	$89.10
Purchase #2	$61.80	3.164%	$63.7554	$63.76	$63.75	$63.80
Purchase #3	$82.64	10.688%	$91.4726	$91.47	$91.45	$91.50
Purchase #4	$55.30	11.147%	$61.4643	$61.46	$61.45	$61.50
Purchase #5	$11.29	6.574%	$12.0322	$12.03	$12.05	$12.00
Purchase #6	$65.46	3.397%	$67.6837	$67.68	$67.70	$67.70
Purchase #7	$57.68	10.519%	$63.7474	$63.75	$63.75	$63.70
7 purchase totals =	$419.56		$449.2678	$449.26	$449.25	$449.30