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	$107.53	6.255%	$114.256	$114.26	$114.25	$114.30
Purchase #2	$95.59	4.554%	$99.9432	$99.94	$99.95	$99.90
Purchase #3	$23.60	8.481%	$25.6015	$25.60	$25.60	$25.60
Purchase #4	$55.26	12.778%	$62.3211	$62.32	$62.30	$62.30
Purchase #5	$39.87	4.651%	$41.7244	$41.72	$41.70	$41.70
Purchase #6	$52.68	13.613%	$59.8513	$59.85	$59.85	$59.90
Purchase #7	$248.95	3.186%	$256.8815	$256.88	$256.90	$256.90
7 purchase totals =	$623.48		$660.5790	$660.57	$660.55	$660.60