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	$116.37	11.375%	$129.6071	$129.61	$129.60	$129.60
Purchase #2	$239.34	13.246%	$271.043	$271.04	$271.05	$271.00
Purchase #3	$177.72	3.225%	$183.4515	$183.45	$183.45	$183.50
Purchase #4	$171.69	12.379%	$192.9435	$192.94	$192.95	$192.90
Purchase #5	$142.66	9.189%	$155.769	$155.77	$155.75	$155.80
Purchase #6	$65.73	10.210%	$72.441	$72.44	$72.45	$72.40
Purchase #7	$72.74	13.649%	$82.6683	$82.67	$82.65	$82.70
7 purchase totals =	$986.25		$1,087.9234	$1,087.92	$1,087.90	$1,087.90