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	$214.66	3.652%	$222.4994	$222.50	$222.50	$222.50
Purchase #2	$200.70	11.797%	$224.3766	$224.38	$224.40	$224.40
Purchase #3	$111.33	13.826%	$126.7225	$126.72	$126.70	$126.70
Purchase #4	$105.71	9.667%	$115.929	$115.93	$115.95	$115.90
Purchase #5	$59.82	5.102%	$62.872	$62.87	$62.85	$62.90
Purchase #6	$31.87	12.832%	$35.9596	$35.96	$35.95	$36.00
Purchase #7	$100.47	4.723%	$105.2152	$105.22	$105.20	$105.20
7 purchase totals =	$824.56		$893.5743	$893.58	$893.55	$893.60