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	$59.65	4.747%	$62.4816	$62.48	$62.50	$62.50
Purchase #2	$235.78	13.623%	$267.9003	$267.90	$267.90	$267.90
Purchase #3	$88.44	8.396%	$95.8654	$95.87	$95.85	$95.90
Purchase #4	$69.54	4.206%	$72.4649	$72.46	$72.45	$72.50
Purchase #5	$56.40	6.536%	$60.0863	$60.09	$60.10	$60.10
Purchase #6	$117.54	11.832%	$131.4473	$131.45	$131.45	$131.40
Purchase #7	$65.69	12.102%	$73.6398	$73.64	$73.65	$73.60
7 purchase totals =	$693.04		$763.8856	$763.89	$763.90	$763.90