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	$235.60	7.577%	$253.4514	$253.45	$253.45	$253.50
Purchase #2	$241.43	5.587%	$254.9187	$254.92	$254.90	$254.90
Purchase #3	$94.80	11.613%	$105.8091	$105.81	$105.80	$105.80
Purchase #4	$178.74	11.264%	$198.8733	$198.87	$198.85	$198.90
Purchase #5	$112.62	3.527%	$116.5921	$116.59	$116.60	$116.60
Purchase #6	$47.57	4.221%	$49.5779	$49.58	$49.60	$49.60
Purchase #7	$19.25	7.516%	$20.6968	$20.70	$20.70	$20.70
7 purchase totals =	$930.01		$999.9193	$999.92	$999.90	$1,000.00