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	$129.94	7.388%	$139.54	$139.54	$139.55	$139.50
Purchase #2	$131.72	4.231%	$137.2931	$137.29	$137.30	$137.30
Purchase #3	$70.90	7.182%	$75.992	$75.99	$76.00	$76.00
Purchase #4	$225.31	3.699%	$233.6442	$233.64	$233.65	$233.60
Purchase #5	$30.88	8.473%	$33.4965	$33.50	$33.50	$33.50
Purchase #6	$241.57	12.129%	$270.87	$270.87	$270.85	$270.90
Purchase #7	$46.86	6.211%	$49.7705	$49.77	$49.75	$49.80
7 purchase totals =	$877.18		$940.6063	$940.60	$940.60	$940.60