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	$40.58	11.552%	$45.2678	$45.27	$45.25	$45.30
Purchase #2	$200.28	10.231%	$220.7706	$220.77	$220.75	$220.80
Purchase #3	$139.34	4.678%	$145.8583	$145.86	$145.85	$145.90
Purchase #4	$95.60	8.286%	$103.5214	$103.52	$103.50	$103.50
Purchase #5	$6.63	5.669%	$7.0059	$7.01	$7.00	$7.00
Purchase #6	$174.29	12.148%	$195.4627	$195.46	$195.45	$195.50
Purchase #7	$60.92	7.773%	$65.6553	$65.66	$65.65	$65.70
7 purchase totals =	$717.64		$783.5420	$783.55	$783.45	$783.70