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	$38.63	10.286%	$42.6035	$42.60	$42.60	$42.60
Purchase #2	$66.99	5.333%	$70.5626	$70.56	$70.55	$70.60
Purchase #3	$159.65	11.465%	$177.9539	$177.95	$177.95	$178.00
Purchase #4	$222.76	10.233%	$245.555	$245.56	$245.55	$245.60
Purchase #5	$210.85	13.263%	$238.815	$238.82	$238.80	$238.80
Purchase #6	$51.29	8.178%	$55.4845	$55.48	$55.50	$55.50
Purchase #7	$225.62	5.826%	$238.7646	$238.76	$238.75	$238.80
7 purchase totals =	$975.79		$1,069.7391	$1,069.73	$1,069.70	$1,069.90