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	$56.71	10.853%	$62.8647	$62.86	$62.85	$62.90
Purchase #2	$71.82	10.574%	$79.4142	$79.41	$79.40	$79.40
Purchase #3	$18.53	8.521%	$20.1089	$20.11	$20.10	$20.10
Purchase #4	$66.72	3.828%	$69.274	$69.27	$69.25	$69.30
Purchase #5	$184.79	13.444%	$209.6332	$209.63	$209.65	$209.60
Purchase #6	$62.60	4.762%	$65.581	$65.58	$65.60	$65.60
Purchase #7	$139.82	5.860%	$148.0135	$148.01	$148.00	$148.00
7 purchase totals =	$600.99		$654.8895	$654.87	$654.85	$654.90