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	$201.55	9.599%	$220.8968	$220.90	$220.90	$220.90
Purchase #2	$60.83	9.257%	$66.461	$66.46	$66.45	$66.50
Purchase #3	$109.58	13.142%	$123.981	$123.98	$124.00	$124.00
Purchase #4	$140.61	5.299%	$148.0609	$148.06	$148.05	$148.10
Purchase #5	$156.94	10.118%	$172.8192	$172.82	$172.80	$172.80
Purchase #6	$158.58	9.189%	$173.1519	$173.15	$173.15	$173.20
Purchase #7	$214.80	13.322%	$243.4157	$243.42	$243.40	$243.40
7 purchase totals =	$1,042.89		$1,148.7865	$1,148.79	$1,148.75	$1,148.90