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	$52.88	11.829%	$59.1352	$59.14	$59.15	$59.10
Purchase #2	$227.30	7.568%	$244.5021	$244.50	$244.50	$244.50
Purchase #3	$126.95	10.178%	$139.871	$139.87	$139.85	$139.90
Purchase #4	$176.46	7.803%	$190.2292	$190.23	$190.25	$190.20
Purchase #5	$27.87	11.211%	$30.9945	$30.99	$31.00	$31.00
Purchase #6	$107.32	9.271%	$117.2696	$117.27	$117.25	$117.30
Purchase #7	$150.52	12.620%	$169.5156	$169.52	$169.50	$169.50
7 purchase totals =	$869.30		$951.5172	$951.52	$951.50	$951.50