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	$236.78	6.661%	$252.5519	$252.55	$252.55	$252.60
Purchase #2	$51.89	9.572%	$56.8569	$56.86	$56.85	$56.90
Purchase #3	$169.88	4.173%	$176.9691	$176.97	$176.95	$177.00
Purchase #4	$217.66	4.469%	$227.3872	$227.39	$227.40	$227.40
Purchase #5	$93.92	10.661%	$103.9328	$103.93	$103.95	$103.90
Purchase #6	$157.31	9.628%	$172.4558	$172.46	$172.45	$172.50
Purchase #7	$50.87	11.826%	$56.8859	$56.89	$56.90	$56.90
7 purchase totals =	$978.31		$1,047.0396	$1,047.05	$1,047.05	$1,047.20