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	$143.63	7.244%	$154.0346	$154.03	$154.05	$154.00
Purchase #2	$172.94	8.510%	$187.6572	$187.66	$187.65	$187.70
Purchase #3	$125.78	12.336%	$141.2962	$141.30	$141.30	$141.30
Purchase #4	$246.27	9.465%	$269.5795	$269.58	$269.60	$269.60
Purchase #5	$242.82	11.796%	$271.463	$271.46	$271.45	$271.50
Purchase #6	$242.98	5.147%	$255.4862	$255.49	$255.50	$255.50
Purchase #7	$18.47	12.644%	$20.8053	$20.81	$20.80	$20.80
7 purchase totals =	$1,192.89		$1,300.3220	$1,300.33	$1,300.35	$1,300.40