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	$239.88	9.555%	$262.8005	$262.80	$262.80	$262.80
Purchase #2	$220.66	4.477%	$230.5389	$230.54	$230.55	$230.50
Purchase #3	$185.37	13.720%	$210.8028	$210.80	$210.80	$210.80
Purchase #4	$197.30	9.779%	$216.594	$216.59	$216.60	$216.60
Purchase #5	$231.78	10.147%	$255.2987	$255.30	$255.30	$255.30
Purchase #6	$51.52	4.196%	$53.6818	$53.68	$53.70	$53.70
Purchase #7	$155.37	10.302%	$171.3762	$171.38	$171.40	$171.40
7 purchase totals =	$1,281.88		$1,401.0929	$1,401.09	$1,401.15	$1,401.10