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	$181.86	10.348%	$200.6789	$200.68	$200.70	$200.70
Purchase #2	$80.45	10.798%	$89.137	$89.14	$89.15	$89.10
Purchase #3	$99.66	4.620%	$104.2643	$104.26	$104.25	$104.30
Purchase #4	$126.33	4.407%	$131.8974	$131.90	$131.90	$131.90
Purchase #5	$8.91	11.477%	$9.9326	$9.93	$9.95	$9.90
Purchase #6	$92.67	8.634%	$100.6711	$100.67	$100.65	$100.70
Purchase #7	$212.58	4.714%	$222.601	$222.60	$222.60	$222.60
7 purchase totals =	$802.46		$859.1823	$859.18	$859.20	$859.20