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	$68.49	12.267%	$76.8917	$76.89	$76.90	$76.90
Purchase #2	$130.90	6.558%	$139.4844	$139.48	$139.50	$139.50
Purchase #3	$112.70	4.423%	$117.6847	$117.68	$117.70	$117.70
Purchase #4	$105.72	5.109%	$111.1212	$111.12	$111.10	$111.10
Purchase #5	$35.41	8.213%	$38.3182	$38.32	$38.30	$38.30
Purchase #6	$62.43	8.460%	$67.7116	$67.71	$67.70	$67.70
Purchase #7	$59.66	5.128%	$62.7194	$62.72	$62.70	$62.70
7 purchase totals =	$575.31		$613.9312	$613.92	$613.90	$613.90