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	$59.58	13.786%	$67.7937	$67.79	$67.80	$67.80
Purchase #2	$139.87	8.516%	$151.7813	$151.78	$151.80	$151.80
Purchase #3	$142.28	3.193%	$146.823	$146.82	$146.80	$146.80
Purchase #4	$108.27	9.829%	$118.9119	$118.91	$118.90	$118.90
Purchase #5	$142.75	9.378%	$156.1371	$156.14	$156.15	$156.10
Purchase #6	$239.29	11.171%	$266.0211	$266.02	$266.00	$266.00
Purchase #7	$104.95	11.399%	$116.9133	$116.91	$116.90	$116.90
7 purchase totals =	$936.99		$1,024.3814	$1,024.37	$1,024.35	$1,024.30