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	$186.74	5.140%	$196.3384	$196.34	$196.35	$196.30
Purchase #2	$162.62	10.311%	$179.3877	$179.39	$179.40	$179.40
Purchase #3	$231.43	4.173%	$241.0876	$241.09	$241.10	$241.10
Purchase #4	$15.86	11.363%	$17.6622	$17.66	$17.65	$17.70
Purchase #5	$99.76	6.189%	$105.9341	$105.93	$105.95	$105.90
Purchase #6	$168.27	13.489%	$190.9679	$190.97	$190.95	$191.00
Purchase #7	$194.96	5.399%	$205.4859	$205.49	$205.50	$205.50
7 purchase totals =	$1,059.64		$1,136.8638	$1,136.87	$1,136.90	$1,136.90