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	$29.95	10.511%	$33.098	$33.10	$33.10	$33.10
Purchase #2	$228.65	11.791%	$255.6101	$255.61	$255.60	$255.60
Purchase #3	$168.32	13.382%	$190.8446	$190.84	$190.85	$190.80
Purchase #4	$68.25	12.275%	$76.6277	$76.63	$76.65	$76.60
Purchase #5	$89.86	5.314%	$94.6352	$94.64	$94.65	$94.60
Purchase #6	$130.75	6.730%	$139.5495	$139.55	$139.55	$139.50
Purchase #7	$246.86	4.720%	$258.5118	$258.51	$258.50	$258.50
7 purchase totals =	$962.64		$1,048.8769	$1,048.88	$1,048.90	$1,048.70