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	$95.48	6.593%	$101.775	$101.78	$101.80	$101.80
Purchase #2	$52.51	13.709%	$59.7086	$59.71	$59.70	$59.70
Purchase #3	$140.75	9.848%	$154.6111	$154.61	$154.60	$154.60
Purchase #4	$104.94	6.181%	$111.4263	$111.43	$111.45	$111.40
Purchase #5	$88.72	12.788%	$100.0655	$100.07	$100.05	$100.10
Purchase #6	$204.98	6.381%	$218.0598	$218.06	$218.05	$218.10
Purchase #7	$211.39	3.861%	$219.5518	$219.55	$219.55	$219.60
7 purchase totals =	$898.77		$965.1981	$965.21	$965.20	$965.30