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	$48.82	11.345%	$54.3586	$54.36	$54.35	$54.40
Purchase #2	$110.51	11.314%	$123.0131	$123.01	$123.00	$123.00
Purchase #3	$74.53	6.315%	$79.2366	$79.24	$79.25	$79.20
Purchase #4	$54.26	12.257%	$60.9106	$60.91	$60.90	$60.90
Purchase #5	$13.95	4.593%	$14.5907	$14.59	$14.60	$14.60
Purchase #6	$29.96	9.216%	$32.7211	$32.72	$32.70	$32.70
Purchase #7	$9.75	13.468%	$11.0631	$11.06	$11.05	$11.10
7 purchase totals =	$341.78		$375.8938	$375.89	$375.85	$375.90