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	$127.89	9.194%	$139.6482	$139.65	$139.65	$139.60
Purchase #2	$214.62	3.855%	$222.8936	$222.89	$222.90	$222.90
Purchase #3	$191.99	13.442%	$217.7973	$217.80	$217.80	$217.80
Purchase #4	$122.92	11.176%	$136.6575	$136.66	$136.65	$136.70
Purchase #5	$201.60	11.246%	$224.2719	$224.27	$224.25	$224.30
Purchase #6	$40.77	3.768%	$42.3062	$42.31	$42.30	$42.30
Purchase #7	$40.35	3.601%	$41.803	$41.80	$41.80	$41.80
7 purchase totals =	$940.14		$1,025.3777	$1,025.38	$1,025.35	$1,025.40