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	$233.58	3.770%	$242.386	$242.39	$242.40	$242.40
Purchase #2	$45.87	6.391%	$48.8016	$48.80	$48.80	$48.80
Purchase #3	$213.82	4.182%	$222.762	$222.76	$222.75	$222.80
Purchase #4	$11.78	6.669%	$12.5656	$12.57	$12.55	$12.60
Purchase #5	$130.89	11.330%	$145.7198	$145.72	$145.70	$145.70
Purchase #6	$193.35	10.225%	$213.12	$213.12	$213.10	$213.10
Purchase #7	$161.55	8.744%	$175.6759	$175.68	$175.70	$175.70
7 purchase totals =	$990.84		$1,061.0309	$1,061.04	$1,061.00	$1,061.10