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	$193.61	6.208%	$205.6293	$205.63	$205.65	$205.60
Purchase #2	$107.79	8.121%	$116.5436	$116.54	$116.55	$116.50
Purchase #3	$168.89	6.534%	$179.9253	$179.93	$179.95	$179.90
Purchase #4	$39.50	7.272%	$42.3724	$42.37	$42.35	$42.40
Purchase #5	$49.55	3.868%	$51.4666	$51.47	$51.45	$51.50
Purchase #6	$107.26	5.262%	$112.904	$112.90	$112.90	$112.90
Purchase #7	$235.70	8.287%	$255.2325	$255.23	$255.25	$255.20
7 purchase totals =	$902.30		$964.0737	$964.07	$964.10	$964.00