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	$214.94	12.140%	$241.0337	$241.03	$241.05	$241.00
Purchase #2	$80.26	11.825%	$89.7507	$89.75	$89.75	$89.80
Purchase #3	$40.77	9.855%	$44.7879	$44.79	$44.80	$44.80
Purchase #4	$138.85	13.437%	$157.5073	$157.51	$157.50	$157.50
Purchase #5	$233.32	4.433%	$243.6631	$243.66	$243.65	$243.70
Purchase #6	$68.36	6.422%	$72.7501	$72.75	$72.75	$72.80
Purchase #7	$93.81	6.340%	$99.7576	$99.76	$99.75	$99.80
7 purchase totals =	$870.31		$949.2504	$949.25	$949.25	$949.40