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	$124.81	6.612%	$133.0624	$133.06	$133.05	$133.10
Purchase #2	$171.70	10.295%	$189.3765	$189.38	$189.40	$189.40
Purchase #3	$187.43	8.476%	$203.3166	$203.32	$203.30	$203.30
Purchase #4	$130.59	10.159%	$143.8566	$143.86	$143.85	$143.90
Purchase #5	$72.90	13.117%	$82.4623	$82.46	$82.45	$82.50
Purchase #6	$177.30	5.116%	$186.3707	$186.37	$186.35	$186.40
Purchase #7	$118.37	12.686%	$133.3864	$133.39	$133.40	$133.40
7 purchase totals =	$983.10		$1,071.8315	$1,071.84	$1,071.80	$1,072.00