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	$66.58	9.425%	$72.8552	$72.86	$72.85	$72.90
Purchase #2	$234.78	7.574%	$252.5622	$252.56	$252.55	$252.60
Purchase #3	$67.90	7.314%	$72.8662	$72.87	$72.85	$72.90
Purchase #4	$194.75	5.174%	$204.8264	$204.83	$204.85	$204.80
Purchase #5	$100.64	12.117%	$112.8345	$112.83	$112.85	$112.80
Purchase #6	$142.79	8.791%	$155.3427	$155.34	$155.35	$155.30
Purchase #7	$117.43	9.600%	$128.7033	$128.70	$128.70	$128.70
7 purchase totals =	$924.87		$999.9905	$999.99	$1,000.00	$1,000.00