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	$56.70	3.606%	$58.7446	$58.74	$58.75	$58.70
Purchase #2	$105.92	5.613%	$111.8653	$111.87	$111.85	$111.90
Purchase #3	$186.77	7.224%	$200.2623	$200.26	$200.25	$200.30
Purchase #4	$177.88	10.378%	$196.3404	$196.34	$196.35	$196.30
Purchase #5	$214.49	6.340%	$228.0887	$228.09	$228.10	$228.10
Purchase #6	$64.78	10.825%	$71.7924	$71.79	$71.80	$71.80
Purchase #7	$227.79	10.460%	$251.6168	$251.62	$251.60	$251.60
7 purchase totals =	$1,034.33		$1,118.7105	$1,118.71	$1,118.70	$1,118.70