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	$221.84	6.144%	$235.4698	$235.47	$235.45	$235.50
Purchase #2	$124.99	7.551%	$134.428	$134.43	$134.45	$134.40
Purchase #3	$94.48	5.682%	$99.8484	$99.85	$99.85	$99.80
Purchase #4	$174.83	7.498%	$187.9388	$187.94	$187.95	$187.90
Purchase #5	$175.99	8.181%	$190.3877	$190.39	$190.40	$190.40
Purchase #6	$153.95	13.831%	$175.2428	$175.24	$175.25	$175.20
Purchase #7	$37.36	3.335%	$38.606	$38.61	$38.60	$38.60
7 purchase totals =	$983.44		$1,061.9215	$1,061.93	$1,061.95	$1,061.80