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	$214.56	11.334%	$238.8782	$238.88	$238.90	$238.90
Purchase #2	$138.28	5.218%	$145.4955	$145.50	$145.50	$145.50
Purchase #3	$129.54	12.397%	$145.5991	$145.60	$145.60	$145.60
Purchase #4	$186.92	6.286%	$198.6698	$198.67	$198.65	$198.70
Purchase #5	$42.71	7.730%	$46.0115	$46.01	$46.00	$46.00
Purchase #6	$45.59	10.700%	$50.4681	$50.47	$50.45	$50.50
Purchase #7	$187.57	4.429%	$195.8775	$195.88	$195.90	$195.90
7 purchase totals =	$945.17		$1,020.9997	$1,021.01	$1,021.00	$1,021.10