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	$230.32	11.313%	$256.3761	$256.38	$256.40	$256.40
Purchase #2	$242.70	7.749%	$261.5068	$261.51	$261.50	$261.50
Purchase #3	$45.76	7.366%	$49.1307	$49.13	$49.15	$49.10
Purchase #4	$92.66	8.815%	$100.828	$100.83	$100.85	$100.80
Purchase #5	$16.46	9.854%	$18.082	$18.08	$18.10	$18.10
Purchase #6	$142.79	12.233%	$160.2575	$160.26	$160.25	$160.30
Purchase #7	$157.92	9.185%	$172.425	$172.43	$172.45	$172.40
7 purchase totals =	$928.61		$1,018.6061	$1,018.62	$1,018.70	$1,018.60