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	$182.67	12.453%	$205.4179	$205.42	$205.40	$205.40
Purchase #2	$107.36	3.438%	$111.051	$111.05	$111.05	$111.10
Purchase #3	$155.86	10.866%	$172.7957	$172.80	$172.80	$172.80
Purchase #4	$24.99	9.203%	$27.2898	$27.29	$27.30	$27.30
Purchase #5	$53.43	11.324%	$59.4804	$59.48	$59.50	$59.50
Purchase #6	$65.87	10.231%	$72.6092	$72.61	$72.60	$72.60
Purchase #7	$42.47	11.252%	$47.2487	$47.25	$47.25	$47.20
7 purchase totals =	$632.65		$695.8927	$695.90	$695.90	$695.90