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	$110.65	5.178%	$116.3795	$116.38	$116.40	$116.40
Purchase #2	$118.57	6.271%	$126.0055	$126.01	$126.00	$126.00
Purchase #3	$59.83	6.143%	$63.5054	$63.51	$63.50	$63.50
Purchase #4	$85.60	7.347%	$91.889	$91.89	$91.90	$91.90
Purchase #5	$27.98	9.176%	$30.5474	$30.55	$30.55	$30.50
Purchase #6	$176.60	11.476%	$196.8666	$196.87	$196.85	$196.90
Purchase #7	$54.62	10.305%	$60.2486	$60.25	$60.25	$60.20
7 purchase totals =	$633.85		$685.4420	$685.46	$685.45	$685.40