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	$209.89	12.796%	$236.7475	$236.75	$236.75	$236.70
Purchase #2	$140.59	10.858%	$155.8553	$155.86	$155.85	$155.90
Purchase #3	$147.29	6.519%	$156.8918	$156.89	$156.90	$156.90
Purchase #4	$10.57	4.831%	$11.0806	$11.08	$11.10	$11.10
Purchase #5	$133.52	6.170%	$141.7582	$141.76	$141.75	$141.80
Purchase #6	$18.53	11.240%	$20.6128	$20.61	$20.60	$20.60
Purchase #7	$13.71	9.762%	$15.0484	$15.05	$15.05	$15.00
7 purchase totals =	$674.10		$737.9946	$738.00	$738.00	$738.00