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	$77.38	11.484%	$86.2663	$86.27	$86.25	$86.30
Purchase #2	$241.60	4.812%	$253.2258	$253.23	$253.25	$253.20
Purchase #3	$49.94	7.337%	$53.6041	$53.60	$53.60	$53.60
Purchase #4	$60.57	9.834%	$66.5265	$66.53	$66.55	$66.50
Purchase #5	$126.26	10.696%	$139.7648	$139.76	$139.75	$139.80
Purchase #6	$108.38	7.428%	$116.4305	$116.43	$116.45	$116.40
Purchase #7	$111.90	13.351%	$126.8398	$126.84	$126.85	$126.80
7 purchase totals =	$776.03		$842.6578	$842.66	$842.70	$842.60