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	$62.61	8.369%	$67.8498	$67.85	$67.85	$67.80
Purchase #2	$83.78	12.502%	$94.2542	$94.25	$94.25	$94.30
Purchase #3	$34.92	13.165%	$39.5172	$39.52	$39.50	$39.50
Purchase #4	$246.89	13.504%	$280.23	$280.23	$280.25	$280.20
Purchase #5	$88.63	13.748%	$100.8149	$100.81	$100.80	$100.80
Purchase #6	$186.52	9.738%	$204.6833	$204.68	$204.70	$204.70
Purchase #7	$245.66	3.180%	$253.472	$253.47	$253.45	$253.50
7 purchase totals =	$949.01		$1,040.8214	$1,040.81	$1,040.80	$1,040.80