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	$203.61	12.116%	$228.2794	$228.28	$228.30	$228.30
Purchase #2	$245.66	6.763%	$262.274	$262.27	$262.25	$262.30
Purchase #3	$47.31	3.741%	$49.0799	$49.08	$49.10	$49.10
Purchase #4	$9.29	12.856%	$10.4843	$10.48	$10.50	$10.50
Purchase #5	$52.66	3.495%	$54.5005	$54.50	$54.50	$54.50
Purchase #6	$247.50	9.441%	$270.8665	$270.87	$270.85	$270.90
Purchase #7	$124.90	5.583%	$131.8732	$131.87	$131.85	$131.90
7 purchase totals =	$930.93		$1,007.3578	$1,007.35	$1,007.35	$1,007.50