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	$143.40	5.485%	$151.2655	$151.27	$151.25	$151.30
Purchase #2	$79.30	13.415%	$89.9381	$89.94	$89.95	$89.90
Purchase #3	$9.73	5.736%	$10.2881	$10.29	$10.30	$10.30
Purchase #4	$179.83	10.599%	$198.8902	$198.89	$198.90	$198.90
Purchase #5	$16.30	3.478%	$16.8669	$16.87	$16.85	$16.90
Purchase #6	$62.30	6.873%	$66.5819	$66.58	$66.60	$66.60
Purchase #7	$247.78	13.307%	$280.7521	$280.75	$280.75	$280.80
7 purchase totals =	$738.64		$814.5828	$814.59	$814.60	$814.70