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	$96.86	10.231%	$106.7697	$106.77	$106.75	$106.80
Purchase #2	$141.71	12.626%	$159.6023	$159.60	$159.60	$159.60
Purchase #3	$132.79	5.335%	$139.8743	$139.87	$139.85	$139.90
Purchase #4	$244.33	4.692%	$255.794	$255.79	$255.80	$255.80
Purchase #5	$152.27	8.370%	$165.015	$165.02	$165.00	$165.00
Purchase #6	$19.62	8.723%	$21.3315	$21.33	$21.35	$21.30
Purchase #7	$230.60	8.318%	$249.7813	$249.78	$249.80	$249.80
7 purchase totals =	$1,018.18		$1,098.1681	$1,098.16	$1,098.15	$1,098.20