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	$68.58	3.165%	$70.7506	$70.75	$70.75	$70.80
Purchase #2	$213.61	11.123%	$237.3698	$237.37	$237.35	$237.40
Purchase #3	$112.56	9.159%	$122.8694	$122.87	$122.85	$122.90
Purchase #4	$100.70	10.410%	$111.1829	$111.18	$111.20	$111.20
Purchase #5	$247.86	5.244%	$260.8578	$260.86	$260.85	$260.90
Purchase #6	$249.72	12.290%	$280.4106	$280.41	$280.40	$280.40
Purchase #7	$12.46	7.132%	$13.3486	$13.35	$13.35	$13.30
7 purchase totals =	$1,005.49		$1,096.7897	$1,096.79	$1,096.75	$1,096.90