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	$177.97	10.644%	$196.9131	$196.91	$196.90	$196.90
Purchase #2	$20.32	5.481%	$21.4337	$21.43	$21.45	$21.40
Purchase #3	$117.52	12.805%	$132.5684	$132.57	$132.55	$132.60
Purchase #4	$210.26	13.560%	$238.7713	$238.77	$238.75	$238.80
Purchase #5	$31.85	6.103%	$33.7938	$33.79	$33.80	$33.80
Purchase #6	$204.59	6.175%	$217.2234	$217.22	$217.20	$217.20
Purchase #7	$61.37	10.778%	$67.9845	$67.98	$68.00	$68.00
7 purchase totals =	$823.88		$908.6882	$908.67	$908.65	$908.70