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	$40.32	11.436%	$44.931	$44.93	$44.95	$44.90
Purchase #2	$40.59	11.520%	$45.266	$45.27	$45.25	$45.30
Purchase #3	$131.87	8.453%	$143.017	$143.02	$143.00	$143.00
Purchase #4	$41.79	5.389%	$44.0421	$44.04	$44.05	$44.00
Purchase #5	$86.75	4.492%	$90.6468	$90.65	$90.65	$90.60
Purchase #6	$127.31	13.437%	$144.4166	$144.42	$144.40	$144.40
Purchase #7	$148.78	5.854%	$157.4896	$157.49	$157.50	$157.50
7 purchase totals =	$617.41		$669.8091	$669.82	$669.80	$669.70