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	$237.53	11.810%	$265.5823	$265.58	$265.60	$265.60
Purchase #2	$143.59	5.608%	$151.6425	$151.64	$151.65	$151.60
Purchase #3	$205.27	8.556%	$222.8329	$222.83	$222.85	$222.80
Purchase #4	$214.70	8.586%	$233.1341	$233.13	$233.15	$233.10
Purchase #5	$146.99	3.360%	$151.9289	$151.93	$151.95	$151.90
Purchase #6	$51.41	5.557%	$54.2669	$54.27	$54.25	$54.30
Purchase #7	$12.60	9.182%	$13.7569	$13.76	$13.75	$13.80
7 purchase totals =	$1,012.09		$1,093.1445	$1,093.14	$1,093.20	$1,093.10