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	$85.54	11.783%	$95.6192	$95.62	$95.60	$95.60
Purchase #2	$110.52	11.543%	$123.2773	$123.28	$123.30	$123.30
Purchase #3	$244.38	12.384%	$274.644	$274.64	$274.65	$274.60
Purchase #4	$128.87	10.347%	$142.2042	$142.20	$142.20	$142.20
Purchase #5	$141.34	9.187%	$154.3249	$154.32	$154.30	$154.30
Purchase #6	$226.27	9.594%	$247.9783	$247.98	$248.00	$248.00
Purchase #7	$24.35	12.597%	$27.4174	$27.42	$27.40	$27.40
7 purchase totals =	$961.27		$1,065.4653	$1,065.46	$1,065.45	$1,065.40