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	$31.70	6.712%	$33.8277	$33.83	$33.85	$33.80
Purchase #2	$129.39	6.554%	$137.8702	$137.87	$137.85	$137.90
Purchase #3	$190.55	7.535%	$204.9079	$204.91	$204.90	$204.90
Purchase #4	$238.64	5.845%	$252.5885	$252.59	$252.60	$252.60
Purchase #5	$51.31	3.788%	$53.2536	$53.25	$53.25	$53.30
Purchase #6	$54.58	11.644%	$60.9353	$60.94	$60.95	$60.90
Purchase #7	$198.90	4.811%	$208.4691	$208.47	$208.45	$208.50
7 purchase totals =	$895.07		$951.8523	$951.86	$951.85	$951.90