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	$111.27	5.859%	$117.7893	$117.79	$117.80	$117.80
Purchase #2	$136.91	8.748%	$148.8869	$148.89	$148.90	$148.90
Purchase #3	$165.29	12.346%	$185.6967	$185.70	$185.70	$185.70
Purchase #4	$58.35	10.582%	$64.5246	$64.52	$64.50	$64.50
Purchase #5	$146.66	3.564%	$151.887	$151.89	$151.90	$151.90
Purchase #6	$99.87	5.113%	$104.9764	$104.98	$105.00	$105.00
Purchase #7	$79.63	11.534%	$88.8145	$88.81	$88.80	$88.80
7 purchase totals =	$797.98		$862.5754	$862.58	$862.60	$862.60