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	$210.33	7.291%	$225.6652	$225.67	$225.65	$225.70
Purchase #2	$85.80	5.353%	$90.3929	$90.39	$90.40	$90.40
Purchase #3	$119.68	11.352%	$133.2661	$133.27	$133.25	$133.30
Purchase #4	$60.58	4.766%	$63.4672	$63.47	$63.45	$63.50
Purchase #5	$147.98	7.171%	$158.5916	$158.59	$158.60	$158.60
Purchase #6	$198.83	13.587%	$225.845	$225.85	$225.85	$225.80
Purchase #7	$240.91	9.189%	$263.0472	$263.05	$263.05	$263.00
7 purchase totals =	$1,064.11		$1,160.2752	$1,160.29	$1,160.25	$1,160.30