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	$88.73	7.461%	$95.3501	$95.35	$95.35	$95.40
Purchase #2	$97.45	7.733%	$104.9858	$104.99	$105.00	$105.00
Purchase #3	$66.71	10.204%	$73.5171	$73.52	$73.50	$73.50
Purchase #4	$49.48	10.278%	$54.5656	$54.57	$54.55	$54.60
Purchase #5	$46.86	5.439%	$49.4087	$49.41	$49.40	$49.40
Purchase #6	$40.72	3.377%	$42.0951	$42.10	$42.10	$42.10
Purchase #7	$132.57	5.570%	$139.9541	$139.95	$139.95	$140.00
7 purchase totals =	$522.52		$559.8765	$559.89	$559.85	$560.00