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	$217.27	7.620%	$233.826	$233.83	$233.85	$233.80
Purchase #2	$160.41	4.839%	$168.1722	$168.17	$168.15	$168.20
Purchase #3	$249.68	12.285%	$280.3532	$280.35	$280.35	$280.40
Purchase #4	$123.30	5.329%	$129.8707	$129.87	$129.85	$129.90
Purchase #5	$51.88	5.246%	$54.6016	$54.60	$54.60	$54.60
Purchase #6	$96.41	7.793%	$103.9232	$103.92	$103.90	$103.90
Purchase #7	$138.74	9.778%	$152.306	$152.31	$152.30	$152.30
7 purchase totals =	$1,037.69		$1,123.0529	$1,123.05	$1,123.00	$1,123.10