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	$95.93	12.558%	$107.9769	$107.98	$108.00	$108.00
Purchase #2	$65.59	10.661%	$72.5825	$72.58	$72.60	$72.60
Purchase #3	$107.52	6.553%	$114.5658	$114.57	$114.55	$114.60
Purchase #4	$136.76	3.235%	$141.1842	$141.18	$141.20	$141.20
Purchase #5	$53.61	4.600%	$56.0761	$56.08	$56.10	$56.10
Purchase #6	$247.89	12.827%	$279.6869	$279.69	$279.70	$279.70
Purchase #7	$78.85	12.520%	$88.722	$88.72	$88.70	$88.70
7 purchase totals =	$786.15		$860.7944	$860.80	$860.85	$860.90