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	$211.99	12.702%	$238.917	$238.92	$238.90	$238.90
Purchase #2	$135.81	9.389%	$148.5612	$148.56	$148.55	$148.60
Purchase #3	$144.67	7.703%	$155.8139	$155.81	$155.80	$155.80
Purchase #4	$170.78	11.553%	$190.5102	$190.51	$190.50	$190.50
Purchase #5	$149.47	7.546%	$160.749	$160.75	$160.75	$160.70
Purchase #6	$20.32	7.416%	$21.8269	$21.83	$21.85	$21.80
Purchase #7	$121.74	7.613%	$131.0081	$131.01	$131.00	$131.00
7 purchase totals =	$954.78		$1,047.3863	$1,047.39	$1,047.35	$1,047.30