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	$162.71	6.303%	$172.9656	$172.97	$172.95	$173.00
Purchase #2	$200.95	3.790%	$208.566	$208.57	$208.55	$208.60
Purchase #3	$70.96	4.824%	$74.3831	$74.38	$74.40	$74.40
Purchase #4	$70.58	3.242%	$72.8682	$72.87	$72.85	$72.90
Purchase #5	$83.29	11.334%	$92.7301	$92.73	$92.75	$92.70
Purchase #6	$103.79	7.617%	$111.6957	$111.70	$111.70	$111.70
Purchase #7	$203.64	12.665%	$229.431	$229.43	$229.45	$229.40
7 purchase totals =	$895.92		$962.6397	$962.65	$962.65	$962.70