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	$195.64	7.369%	$210.0567	$210.06	$210.05	$210.10
Purchase #2	$247.25	8.115%	$267.3143	$267.31	$267.30	$267.30
Purchase #3	$175.69	11.846%	$196.5022	$196.50	$196.50	$196.50
Purchase #4	$208.94	10.609%	$231.1064	$231.11	$231.10	$231.10
Purchase #5	$66.65	8.550%	$72.3486	$72.35	$72.35	$72.30
Purchase #6	$113.72	12.717%	$128.1818	$128.18	$128.20	$128.20
Purchase #7	$104.39	3.840%	$108.3986	$108.40	$108.40	$108.40
7 purchase totals =	$1,112.28		$1,213.9086	$1,213.91	$1,213.90	$1,213.90