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	$62.95	4.313%	$65.665	$65.67	$65.65	$65.70
Purchase #2	$153.98	5.676%	$162.7199	$162.72	$162.70	$162.70
Purchase #3	$218.25	8.760%	$237.3687	$237.37	$237.35	$237.40
Purchase #4	$52.59	13.269%	$59.5682	$59.57	$59.55	$59.60
Purchase #5	$135.55	11.813%	$151.5625	$151.56	$151.55	$151.60
Purchase #6	$48.96	9.676%	$53.6974	$53.70	$53.70	$53.70
Purchase #7	$9.70	10.639%	$10.732	$10.73	$10.75	$10.70
7 purchase totals =	$681.98		$741.3137	$741.32	$741.25	$741.40