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	$63.74	3.421%	$65.9205	$65.92	$65.90	$65.90
Purchase #2	$164.58	4.611%	$172.1688	$172.17	$172.15	$172.20
Purchase #3	$190.78	5.201%	$200.7025	$200.70	$200.70	$200.70
Purchase #4	$103.81	10.679%	$114.8959	$114.90	$114.90	$114.90
Purchase #5	$85.75	3.342%	$88.6158	$88.62	$88.60	$88.60
Purchase #6	$63.60	5.184%	$66.897	$66.90	$66.90	$66.90
Purchase #7	$190.52	12.412%	$214.1673	$214.17	$214.15	$214.20
7 purchase totals =	$862.78		$923.3678	$923.38	$923.30	$923.40