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	$248.71	6.708%	$265.3935	$265.39	$265.40	$265.40
Purchase #2	$187.89	13.282%	$212.8455	$212.85	$212.85	$212.80
Purchase #3	$111.61	10.589%	$123.4284	$123.43	$123.45	$123.40
Purchase #4	$31.66	6.771%	$33.8037	$33.80	$33.80	$33.80
Purchase #5	$80.80	12.140%	$90.6091	$90.61	$90.60	$90.60
Purchase #6	$132.33	13.568%	$150.2845	$150.28	$150.30	$150.30
Purchase #7	$226.53	5.703%	$239.449	$239.45	$239.45	$239.40
7 purchase totals =	$1,019.53		$1,115.8137	$1,115.81	$1,115.85	$1,115.70