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	$214.52	8.303%	$232.3316	$232.33	$232.35	$232.30
Purchase #2	$173.38	12.800%	$195.5726	$195.57	$195.55	$195.60
Purchase #3	$101.88	6.542%	$108.545	$108.55	$108.55	$108.50
Purchase #4	$222.70	10.478%	$246.0345	$246.03	$246.05	$246.00
Purchase #5	$99.94	11.530%	$111.4631	$111.46	$111.45	$111.50
Purchase #6	$33.77	12.127%	$37.8653	$37.87	$37.85	$37.90
Purchase #7	$210.97	4.126%	$219.6746	$219.67	$219.65	$219.70
7 purchase totals =	$1,057.16		$1,151.4867	$1,151.48	$1,151.45	$1,151.50