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	$236.76	6.553%	$252.2749	$252.27	$252.25	$252.30
Purchase #2	$234.77	8.143%	$253.8873	$253.89	$253.90	$253.90
Purchase #3	$127.93	10.428%	$141.2705	$141.27	$141.25	$141.30
Purchase #4	$131.81	5.826%	$139.4893	$139.49	$139.50	$139.50
Purchase #5	$109.95	7.668%	$118.381	$118.38	$118.40	$118.40
Purchase #6	$75.54	10.307%	$83.3259	$83.33	$83.35	$83.30
Purchase #7	$36.64	7.712%	$39.4657	$39.47	$39.45	$39.50
7 purchase totals =	$953.40		$1,028.0946	$1,028.10	$1,028.10	$1,028.20