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	$113.35	5.446%	$119.523	$119.52	$119.50	$119.50
Purchase #2	$124.38	5.699%	$131.4684	$131.47	$131.45	$131.50
Purchase #3	$21.90	4.540%	$22.8943	$22.89	$22.90	$22.90
Purchase #4	$85.44	11.271%	$95.0699	$95.07	$95.05	$95.10
Purchase #5	$73.98	6.677%	$78.9196	$78.92	$78.90	$78.90
Purchase #6	$234.27	13.481%	$265.8519	$265.85	$265.85	$265.90
Purchase #7	$42.46	8.193%	$45.9387	$45.94	$45.95	$45.90
7 purchase totals =	$695.78		$759.6658	$759.66	$759.60	$759.70