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	$233.72	5.545%	$246.6798	$246.68	$246.70	$246.70
Purchase #2	$167.90	13.172%	$190.0158	$190.02	$190.00	$190.00
Purchase #3	$136.94	3.645%	$141.9315	$141.93	$141.95	$141.90
Purchase #4	$30.75	7.269%	$32.9852	$32.99	$33.00	$33.00
Purchase #5	$229.89	11.110%	$255.4308	$255.43	$255.45	$255.40
Purchase #6	$61.74	8.269%	$66.8453	$66.85	$66.85	$66.80
Purchase #7	$100.62	10.396%	$111.0805	$111.08	$111.10	$111.10
7 purchase totals =	$961.56		$1,044.9689	$1,044.98	$1,045.05	$1,044.90