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	$126.31	11.253%	$140.5237	$140.52	$140.50	$140.50
Purchase #2	$138.91	9.198%	$151.6869	$151.69	$151.70	$151.70
Purchase #3	$68.86	4.442%	$71.9188	$71.92	$71.90	$71.90
Purchase #4	$204.72	4.804%	$214.5547	$214.55	$214.55	$214.60
Purchase #5	$178.64	6.868%	$190.909	$190.91	$190.90	$190.90
Purchase #6	$97.38	5.781%	$103.0095	$103.01	$103.00	$103.00
Purchase #7	$85.81	11.504%	$95.6816	$95.68	$95.70	$95.70
7 purchase totals =	$900.63		$968.2842	$968.28	$968.25	$968.30