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	$214.52	4.832%	$224.8856	$224.89	$224.90	$224.90
Purchase #2	$74.90	6.435%	$79.7198	$79.72	$79.70	$79.70
Purchase #3	$120.60	9.179%	$131.6699	$131.67	$131.65	$131.70
Purchase #4	$8.52	11.211%	$9.4752	$9.48	$9.50	$9.50
Purchase #5	$153.94	6.849%	$164.4834	$164.48	$164.50	$164.50
Purchase #6	$244.87	4.242%	$255.2574	$255.26	$255.25	$255.30
Purchase #7	$150.53	12.413%	$169.2153	$169.22	$169.20	$169.20
7 purchase totals =	$967.88		$1,034.7066	$1,034.72	$1,034.70	$1,034.80