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	$133.82	13.821%	$152.3153	$152.32	$152.30	$152.30
Purchase #2	$241.91	4.133%	$251.9081	$251.91	$251.90	$251.90
Purchase #3	$51.41	5.222%	$54.0946	$54.09	$54.10	$54.10
Purchase #4	$142.50	12.716%	$160.6203	$160.62	$160.60	$160.60
Purchase #5	$224.86	13.137%	$254.3999	$254.40	$254.40	$254.40
Purchase #6	$152.63	13.742%	$173.6044	$173.60	$173.60	$173.60
Purchase #7	$34.95	11.389%	$38.9305	$38.93	$38.95	$38.90
7 purchase totals =	$982.08		$1,085.8731	$1,085.87	$1,085.85	$1,085.80