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	$91.42	5.794%	$96.7169	$96.72	$96.70	$96.70
Purchase #2	$66.39	6.322%	$70.5872	$70.59	$70.60	$70.60
Purchase #3	$94.45	10.559%	$104.423	$104.42	$104.40	$104.40
Purchase #4	$244.77	12.618%	$275.6551	$275.66	$275.65	$275.70
Purchase #5	$114.41	8.475%	$124.1062	$124.11	$124.10	$124.10
Purchase #6	$158.88	4.224%	$165.5911	$165.59	$165.60	$165.60
Purchase #7	$208.52	13.114%	$235.8653	$235.87	$235.85	$235.90
7 purchase totals =	$978.84		$1,072.9448	$1,072.96	$1,072.90	$1,073.00