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	$32.72	4.832%	$34.301	$34.30	$34.30	$34.30
Purchase #2	$156.62	10.863%	$173.6336	$173.63	$173.65	$173.60
Purchase #3	$141.83	11.262%	$157.8029	$157.80	$157.80	$157.80
Purchase #4	$135.63	3.833%	$140.8287	$140.83	$140.85	$140.80
Purchase #5	$155.47	7.248%	$166.7385	$166.74	$166.75	$166.70
Purchase #6	$218.52	9.143%	$238.4993	$238.50	$238.50	$238.50
Purchase #7	$87.89	12.698%	$99.0503	$99.05	$99.05	$99.10
7 purchase totals =	$928.68		$1,010.8543	$1,010.85	$1,010.90	$1,010.80