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	$112.55	3.696%	$116.7098	$116.71	$116.70	$116.70
Purchase #2	$92.36	12.704%	$104.0934	$104.09	$104.10	$104.10
Purchase #3	$92.94	7.709%	$100.1047	$100.10	$100.10	$100.10
Purchase #4	$89.25	4.264%	$93.0556	$93.06	$93.05	$93.10
Purchase #5	$166.97	10.550%	$184.5853	$184.59	$184.60	$184.60
Purchase #6	$107.89	5.545%	$113.8725	$113.87	$113.85	$113.90
Purchase #7	$238.69	3.684%	$247.4833	$247.48	$247.50	$247.50
7 purchase totals =	$900.65		$959.9046	$959.90	$959.90	$960.00