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	$107.96	3.408%	$111.6393	$111.64	$111.65	$111.60
Purchase #2	$116.82	10.186%	$128.7193	$128.72	$128.70	$128.70
Purchase #3	$106.99	4.504%	$111.8088	$111.81	$111.80	$111.80
Purchase #4	$82.53	3.853%	$85.7099	$85.71	$85.70	$85.70
Purchase #5	$87.50	8.355%	$94.8106	$94.81	$94.80	$94.80
Purchase #6	$38.45	10.307%	$42.413	$42.41	$42.40	$42.40
Purchase #7	$163.85	9.601%	$179.5812	$179.58	$179.60	$179.60
7 purchase totals =	$704.10		$754.6821	$754.68	$754.65	$754.60