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	$89.72	6.164%	$95.2503	$95.25	$95.25	$95.30
Purchase #2	$79.82	13.473%	$90.5741	$90.57	$90.55	$90.60
Purchase #3	$244.29	12.823%	$275.6153	$275.62	$275.60	$275.60
Purchase #4	$119.33	6.395%	$126.9612	$126.96	$126.95	$127.00
Purchase #5	$74.58	10.208%	$82.1931	$82.19	$82.20	$82.20
Purchase #6	$43.45	12.369%	$48.8243	$48.82	$48.80	$48.80
Purchase #7	$217.47	13.838%	$247.5635	$247.56	$247.55	$247.60
7 purchase totals =	$868.66		$966.9818	$966.97	$966.90	$967.10