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	$81.87	6.836%	$87.4666	$87.47	$87.45	$87.50
Purchase #2	$29.61	7.619%	$31.866	$31.87	$31.85	$31.90
Purchase #3	$113.30	11.347%	$126.1562	$126.16	$126.15	$126.20
Purchase #4	$63.61	4.389%	$66.4018	$66.40	$66.40	$66.40
Purchase #5	$33.28	4.104%	$34.6458	$34.65	$34.65	$34.60
Purchase #6	$228.83	5.518%	$241.4568	$241.46	$241.45	$241.50
Purchase #7	$189.52	5.734%	$200.3871	$200.39	$200.40	$200.40
7 purchase totals =	$740.02		$788.3803	$788.40	$788.35	$788.50