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	$44.95	11.333%	$50.0442	$50.04	$50.05	$50.00
Purchase #2	$29.56	4.262%	$30.8198	$30.82	$30.80	$30.80
Purchase #3	$137.82	9.212%	$150.516	$150.52	$150.50	$150.50
Purchase #4	$95.57	5.439%	$100.7681	$100.77	$100.75	$100.80
Purchase #5	$114.87	4.401%	$119.9254	$119.93	$119.95	$119.90
Purchase #6	$156.85	13.203%	$177.5589	$177.56	$177.55	$177.60
Purchase #7	$92.55	3.144%	$95.4598	$95.46	$95.45	$95.50
7 purchase totals =	$672.17		$725.0922	$725.10	$725.05	$725.10