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	$114.95	11.438%	$128.098	$128.10	$128.10	$128.10
Purchase #2	$65.52	10.363%	$72.3098	$72.31	$72.30	$72.30
Purchase #3	$139.33	12.503%	$156.7504	$156.75	$156.75	$156.80
Purchase #4	$235.30	6.866%	$251.4557	$251.46	$251.45	$251.50
Purchase #5	$95.48	9.406%	$104.4608	$104.46	$104.45	$104.50
Purchase #6	$231.93	6.201%	$246.312	$246.31	$246.30	$246.30
Purchase #7	$124.97	3.175%	$128.9378	$128.94	$128.95	$128.90
7 purchase totals =	$1,007.48		$1,088.3245	$1,088.33	$1,088.30	$1,088.40