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	$215.85	11.106%	$239.8223	$239.82	$239.80	$239.80
Purchase #2	$220.52	9.625%	$241.7451	$241.75	$241.75	$241.70
Purchase #3	$56.52	11.317%	$62.9164	$62.92	$62.90	$62.90
Purchase #4	$155.58	12.781%	$175.4647	$175.46	$175.45	$175.50
Purchase #5	$82.98	3.342%	$85.7532	$85.75	$85.75	$85.80
Purchase #6	$136.40	4.554%	$142.6117	$142.61	$142.60	$142.60
Purchase #7	$118.56	12.470%	$133.3444	$133.34	$133.35	$133.30
7 purchase totals =	$986.41		$1,081.6578	$1,081.65	$1,081.60	$1,081.60