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	$59.55	10.295%	$65.6807	$65.68	$65.70	$65.70
Purchase #2	$13.78	4.517%	$14.4024	$14.40	$14.40	$14.40
Purchase #3	$76.87	11.181%	$85.4648	$85.46	$85.45	$85.50
Purchase #4	$155.88	6.698%	$166.3208	$166.32	$166.30	$166.30
Purchase #5	$140.95	6.428%	$150.0103	$150.01	$150.00	$150.00
Purchase #6	$111.91	3.796%	$116.1581	$116.16	$116.15	$116.20
Purchase #7	$130.83	12.792%	$147.5658	$147.57	$147.55	$147.60
7 purchase totals =	$689.77		$745.6029	$745.60	$745.55	$745.70