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	$144.64	8.699%	$157.2222	$157.22	$157.20	$157.20
Purchase #2	$205.90	5.257%	$216.7242	$216.72	$216.70	$216.70
Purchase #3	$243.39	5.307%	$256.3067	$256.31	$256.30	$256.30
Purchase #4	$181.51	8.235%	$196.4573	$196.46	$196.45	$196.50
Purchase #5	$90.32	11.757%	$100.9389	$100.94	$100.95	$100.90
Purchase #6	$173.88	5.640%	$183.6868	$183.69	$183.70	$183.70
Purchase #7	$135.71	8.553%	$147.3173	$147.32	$147.30	$147.30
7 purchase totals =	$1,175.35		$1,258.6534	$1,258.66	$1,258.60	$1,258.60