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	$95.78	7.639%	$103.0966	$103.10	$103.10	$103.10
Purchase #2	$169.70	4.241%	$176.897	$176.90	$176.90	$176.90
Purchase #3	$119.48	10.815%	$132.4018	$132.40	$132.40	$132.40
Purchase #4	$40.25	12.315%	$45.2068	$45.21	$45.20	$45.20
Purchase #5	$137.28	12.792%	$154.8409	$154.84	$154.85	$154.80
Purchase #6	$232.96	12.683%	$262.5063	$262.51	$262.50	$262.50
Purchase #7	$94.46	6.572%	$100.6679	$100.67	$100.65	$100.70
7 purchase totals =	$889.91		$975.6173	$975.63	$975.60	$975.60