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	$38.93	4.749%	$40.7788	$40.78	$40.80	$40.80
Purchase #2	$119.47	5.244%	$125.735	$125.74	$125.75	$125.70
Purchase #3	$232.55	3.287%	$240.1939	$240.19	$240.20	$240.20
Purchase #4	$185.35	10.451%	$204.7209	$204.72	$204.70	$204.70
Purchase #5	$193.77	3.700%	$200.9395	$200.94	$200.95	$200.90
Purchase #6	$132.27	7.152%	$141.73	$141.73	$141.75	$141.70
Purchase #7	$169.28	12.588%	$190.589	$190.59	$190.60	$190.60
7 purchase totals =	$1,071.62		$1,144.6871	$1,144.69	$1,144.75	$1,144.60