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	$214.62	13.638%	$243.8899	$243.89	$243.90	$243.90
Purchase #2	$93.41	9.860%	$102.6202	$102.62	$102.60	$102.60
Purchase #3	$44.57	4.317%	$46.4941	$46.49	$46.50	$46.50
Purchase #4	$60.38	10.490%	$66.7139	$66.71	$66.70	$66.70
Purchase #5	$166.65	13.351%	$188.8994	$188.90	$188.90	$188.90
Purchase #6	$154.26	3.629%	$159.8581	$159.86	$159.85	$159.90
Purchase #7	$93.79	11.832%	$104.8872	$104.89	$104.90	$104.90
7 purchase totals =	$827.68		$913.3628	$913.36	$913.35	$913.40