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	$73.45	13.451%	$83.3298	$83.33	$83.35	$83.30
Purchase #2	$126.96	13.334%	$143.8888	$143.89	$143.90	$143.90
Purchase #3	$30.78	3.431%	$31.8361	$31.84	$31.85	$31.80
Purchase #4	$52.46	9.127%	$57.248	$57.25	$57.25	$57.20
Purchase #5	$182.52	9.785%	$200.3796	$200.38	$200.40	$200.40
Purchase #6	$120.44	9.188%	$131.506	$131.51	$131.50	$131.50
Purchase #7	$221.65	12.737%	$249.8816	$249.88	$249.90	$249.90
7 purchase totals =	$808.26		$898.0699	$898.08	$898.15	$898.00