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	$208.44	3.327%	$215.3748	$215.37	$215.35	$215.40
Purchase #2	$236.85	7.858%	$255.4617	$255.46	$255.45	$255.50
Purchase #3	$230.56	12.626%	$259.6705	$259.67	$259.65	$259.70
Purchase #4	$95.89	8.137%	$103.6926	$103.69	$103.70	$103.70
Purchase #5	$36.51	13.615%	$41.4808	$41.48	$41.50	$41.50
Purchase #6	$107.40	4.236%	$111.9495	$111.95	$111.95	$111.90
Purchase #7	$38.77	13.623%	$44.0516	$44.05	$44.05	$44.10
7 purchase totals =	$954.42		$1,031.6815	$1,031.67	$1,031.65	$1,031.80