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	$113.33	4.380%	$118.2939	$118.29	$118.30	$118.30
Purchase #2	$139.83	3.316%	$144.4668	$144.47	$144.45	$144.50
Purchase #3	$94.58	4.540%	$98.8739	$98.87	$98.85	$98.90
Purchase #4	$74.62	7.140%	$79.9479	$79.95	$79.95	$79.90
Purchase #5	$64.27	5.421%	$67.7541	$67.75	$67.75	$67.80
Purchase #6	$155.61	13.657%	$176.8617	$176.86	$176.85	$176.90
Purchase #7	$29.66	10.634%	$32.814	$32.81	$32.80	$32.80
7 purchase totals =	$671.90		$719.0123	$719.00	$718.95	$719.10