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	$208.68	3.422%	$215.821	$215.82	$215.80	$215.80
Purchase #2	$220.86	11.686%	$246.6697	$246.67	$246.65	$246.70
Purchase #3	$144.96	11.328%	$161.3811	$161.38	$161.40	$161.40
Purchase #4	$37.93	4.508%	$39.6399	$39.64	$39.65	$39.60
Purchase #5	$64.80	12.472%	$72.8819	$72.88	$72.90	$72.90
Purchase #6	$101.90	10.754%	$112.8583	$112.86	$112.85	$112.90
Purchase #7	$104.48	6.238%	$110.9975	$111.00	$111.00	$111.00
7 purchase totals =	$883.61		$960.2494	$960.25	$960.25	$960.30