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	$217.69	7.870%	$234.8222	$234.82	$234.80	$234.80
Purchase #2	$87.91	3.185%	$90.7099	$90.71	$90.70	$90.70
Purchase #3	$55.64	4.580%	$58.1883	$58.19	$58.20	$58.20
Purchase #4	$92.67	8.741%	$100.7703	$100.77	$100.75	$100.80
Purchase #5	$89.35	13.594%	$101.4962	$101.50	$101.50	$101.50
Purchase #6	$25.91	6.643%	$27.6312	$27.63	$27.65	$27.60
Purchase #7	$12.65	9.688%	$13.8755	$13.88	$13.90	$13.90
7 purchase totals =	$581.82		$627.4936	$627.50	$627.50	$627.50