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	$95.31	4.382%	$99.4865	$99.49	$99.50	$99.50
Purchase #2	$122.95	9.492%	$134.6204	$134.62	$134.60	$134.60
Purchase #3	$122.75	3.450%	$126.9849	$126.98	$127.00	$127.00
Purchase #4	$22.85	8.689%	$24.8354	$24.84	$24.85	$24.80
Purchase #5	$46.35	9.738%	$50.8636	$50.86	$50.85	$50.90
Purchase #6	$122.83	3.788%	$127.4828	$127.48	$127.50	$127.50
Purchase #7	$136.76	10.778%	$151.5	$151.50	$151.50	$151.50
7 purchase totals =	$669.80		$715.7736	$715.77	$715.80	$715.80