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	$126.85	3.755%	$131.6132	$131.61	$131.60	$131.60
Purchase #2	$84.68	12.137%	$94.9576	$94.96	$94.95	$95.00
Purchase #3	$241.76	13.658%	$274.7796	$274.78	$274.80	$274.80
Purchase #4	$100.38	4.754%	$105.1521	$105.15	$105.15	$105.20
Purchase #5	$94.60	13.497%	$107.3682	$107.37	$107.35	$107.40
Purchase #6	$95.68	5.185%	$100.641	$100.64	$100.65	$100.60
Purchase #7	$199.81	5.105%	$210.0103	$210.01	$210.00	$210.00
7 purchase totals =	$943.76		$1,024.5220	$1,024.52	$1,024.50	$1,024.60