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	$85.62	8.153%	$92.6006	$92.60	$92.60	$92.60
Purchase #2	$152.87	13.152%	$172.9755	$172.98	$173.00	$173.00
Purchase #3	$191.50	6.177%	$203.329	$203.33	$203.35	$203.30
Purchase #4	$246.56	10.116%	$271.502	$271.50	$271.50	$271.50
Purchase #5	$85.86	5.574%	$90.6458	$90.65	$90.65	$90.60
Purchase #6	$11.78	7.419%	$12.654	$12.65	$12.65	$12.70
Purchase #7	$141.67	11.484%	$157.9394	$157.94	$157.95	$157.90
7 purchase totals =	$915.86		$1,001.6463	$1,001.65	$1,001.70	$1,001.60