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	$89.29	10.264%	$98.4547	$98.45	$98.45	$98.50
Purchase #2	$47.30	3.428%	$48.9214	$48.92	$48.90	$48.90
Purchase #3	$103.39	6.153%	$109.7516	$109.75	$109.75	$109.80
Purchase #4	$51.52	8.298%	$55.7951	$55.80	$55.80	$55.80
Purchase #5	$16.80	10.193%	$18.5124	$18.51	$18.50	$18.50
Purchase #6	$181.87	7.720%	$195.9104	$195.91	$195.90	$195.90
Purchase #7	$197.37	9.210%	$215.5478	$215.55	$215.55	$215.50
7 purchase totals =	$687.54		$742.8934	$742.89	$742.85	$742.90