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	$184.34	8.523%	$200.0513	$200.05	$200.05	$200.10
Purchase #2	$9.87	4.671%	$10.331	$10.33	$10.35	$10.30
Purchase #3	$167.55	12.205%	$187.9995	$188.00	$188.00	$188.00
Purchase #4	$104.83	11.290%	$116.6653	$116.67	$116.65	$116.70
Purchase #5	$200.94	9.302%	$219.6314	$219.63	$219.65	$219.60
Purchase #6	$80.35	12.250%	$90.1929	$90.19	$90.20	$90.20
Purchase #7	$198.61	12.129%	$222.6994	$222.70	$222.70	$222.70
7 purchase totals =	$946.49		$1,047.5708	$1,047.57	$1,047.60	$1,047.60