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	$106.62	11.434%	$118.8109	$118.81	$118.80	$118.80
Purchase #2	$95.95	12.167%	$107.6242	$107.62	$107.60	$107.60
Purchase #3	$248.59	3.280%	$256.7438	$256.74	$256.75	$256.70
Purchase #4	$245.85	8.126%	$265.8278	$265.83	$265.85	$265.80
Purchase #5	$136.37	8.846%	$148.4333	$148.43	$148.45	$148.40
Purchase #6	$107.63	4.513%	$112.4873	$112.49	$112.50	$112.50
Purchase #7	$123.46	6.591%	$131.5972	$131.60	$131.60	$131.60
7 purchase totals =	$1,064.47		$1,141.5245	$1,141.52	$1,141.55	$1,141.40