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	$236.58	8.375%	$256.3936	$256.39	$256.40	$256.40
Purchase #2	$173.48	11.147%	$192.8178	$192.82	$192.80	$192.80
Purchase #3	$64.75	10.650%	$71.6459	$71.65	$71.65	$71.60
Purchase #4	$61.51	6.839%	$65.7167	$65.72	$65.70	$65.70
Purchase #5	$78.29	9.196%	$85.4895	$85.49	$85.50	$85.50
Purchase #6	$184.81	11.165%	$205.444	$205.44	$205.45	$205.40
Purchase #7	$70.81	8.849%	$77.076	$77.08	$77.10	$77.10
7 purchase totals =	$870.23		$954.5835	$954.59	$954.60	$954.50