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	$48.69	12.732%	$54.8892	$54.89	$54.90	$54.90
Purchase #2	$94.35	11.764%	$105.4493	$105.45	$105.45	$105.40
Purchase #3	$33.76	3.359%	$34.894	$34.89	$34.90	$34.90
Purchase #4	$88.36	5.212%	$92.9653	$92.97	$92.95	$93.00
Purchase #5	$180.76	7.628%	$194.5484	$194.55	$194.55	$194.50
Purchase #6	$125.74	11.103%	$139.7009	$139.70	$139.70	$139.70
Purchase #7	$107.61	3.657%	$111.5453	$111.55	$111.55	$111.50
7 purchase totals =	$679.27		$733.9924	$734.00	$734.00	$733.90