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	$197.62	5.500%	$208.4891	$208.49	$208.50	$208.50
Purchase #2	$111.69	4.328%	$116.5239	$116.52	$116.50	$116.50
Purchase #3	$154.72	13.638%	$175.8207	$175.82	$175.80	$175.80
Purchase #4	$184.43	10.639%	$204.0515	$204.05	$204.05	$204.10
Purchase #5	$155.53	8.555%	$168.8356	$168.84	$168.85	$168.80
Purchase #6	$222.79	7.841%	$240.259	$240.26	$240.25	$240.30
Purchase #7	$33.86	13.728%	$38.5083	$38.51	$38.50	$38.50
7 purchase totals =	$1,060.64		$1,152.4881	$1,152.49	$1,152.45	$1,152.50