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	$182.44	5.439%	$192.3629	$192.36	$192.35	$192.40
Purchase #2	$45.58	6.461%	$48.5249	$48.52	$48.50	$48.50
Purchase #3	$111.47	12.606%	$125.5219	$125.52	$125.50	$125.50
Purchase #4	$54.54	13.102%	$61.6858	$61.69	$61.70	$61.70
Purchase #5	$89.28	5.335%	$94.0431	$94.04	$94.05	$94.00
Purchase #6	$100.28	10.823%	$111.1333	$111.13	$111.15	$111.10
Purchase #7	$16.63	4.798%	$17.4279	$17.43	$17.45	$17.40
7 purchase totals =	$600.22		$650.6998	$650.69	$650.70	$650.60