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	$63.42	3.151%	$65.4184	$65.42	$65.40	$65.40
Purchase #2	$56.47	4.519%	$59.0219	$59.02	$59.00	$59.00
Purchase #3	$78.61	5.389%	$82.8463	$82.85	$82.85	$82.80
Purchase #4	$169.55	12.131%	$190.1181	$190.12	$190.10	$190.10
Purchase #5	$62.29	4.690%	$65.2114	$65.21	$65.20	$65.20
Purchase #6	$98.45	13.693%	$111.9308	$111.93	$111.95	$111.90
Purchase #7	$227.33	12.578%	$255.9236	$255.92	$255.90	$255.90
7 purchase totals =	$756.12		$830.4705	$830.47	$830.40	$830.30