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	$49.27	11.285%	$54.8301	$54.83	$54.85	$54.80
Purchase #2	$196.65	13.251%	$222.7081	$222.71	$222.70	$222.70
Purchase #3	$117.32	13.747%	$133.448	$133.45	$133.45	$133.40
Purchase #4	$48.81	12.485%	$54.9039	$54.90	$54.90	$54.90
Purchase #5	$105.47	3.207%	$108.8524	$108.85	$108.85	$108.90
Purchase #6	$90.95	7.199%	$97.4975	$97.50	$97.50	$97.50
Purchase #7	$54.66	9.790%	$60.0112	$60.01	$60.00	$60.00
7 purchase totals =	$663.13		$732.2512	$732.25	$732.25	$732.20