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	$225.54	7.191%	$241.7586	$241.76	$241.75	$241.80
Purchase #2	$95.40	4.380%	$99.5785	$99.58	$99.60	$99.60
Purchase #3	$199.50	5.143%	$209.7603	$209.76	$209.75	$209.80
Purchase #4	$46.97	12.639%	$52.9065	$52.91	$52.90	$52.90
Purchase #5	$179.28	4.791%	$187.8693	$187.87	$187.85	$187.90
Purchase #6	$121.51	4.340%	$126.7835	$126.78	$126.80	$126.80
Purchase #7	$231.86	7.475%	$249.1915	$249.19	$249.20	$249.20
7 purchase totals =	$1,100.06		$1,167.8482	$1,167.85	$1,167.85	$1,168.00