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	$203.58	8.418%	$220.7174	$220.72	$220.70	$220.70
Purchase #2	$57.53	4.201%	$59.9468	$59.95	$59.95	$59.90
Purchase #3	$144.84	10.536%	$160.1003	$160.10	$160.10	$160.10
Purchase #4	$245.57	9.726%	$269.4541	$269.45	$269.45	$269.50
Purchase #5	$142.68	11.330%	$158.8456	$158.85	$158.85	$158.80
Purchase #6	$85.63	3.280%	$88.4387	$88.44	$88.45	$88.40
Purchase #7	$60.73	7.162%	$65.0795	$65.08	$65.10	$65.10
7 purchase totals =	$940.56		$1,022.5824	$1,022.59	$1,022.60	$1,022.50