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	$224.80	13.725%	$255.6538	$255.65	$255.65	$255.70
Purchase #2	$175.49	5.488%	$185.1209	$185.12	$185.10	$185.10
Purchase #3	$169.56	12.103%	$190.0818	$190.08	$190.10	$190.10
Purchase #4	$89.60	5.171%	$94.2332	$94.23	$94.25	$94.20
Purchase #5	$177.66	11.873%	$198.7536	$198.75	$198.75	$198.80
Purchase #6	$40.41	5.678%	$42.7045	$42.70	$42.70	$42.70
Purchase #7	$175.27	4.665%	$183.4463	$183.45	$183.45	$183.40
7 purchase totals =	$1,052.79		$1,149.9941	$1,149.98	$1,150.00	$1,150.00