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	$57.72	9.405%	$63.1486	$63.15	$63.15	$63.10
Purchase #2	$234.81	12.128%	$263.2878	$263.29	$263.30	$263.30
Purchase #3	$153.40	8.669%	$166.6982	$166.70	$166.70	$166.70
Purchase #4	$54.45	9.805%	$59.7888	$59.79	$59.80	$59.80
Purchase #5	$218.52	9.168%	$238.5539	$238.55	$238.55	$238.60
Purchase #6	$99.95	7.294%	$107.2404	$107.24	$107.25	$107.20
Purchase #7	$50.89	3.723%	$52.7846	$52.78	$52.80	$52.80
7 purchase totals =	$869.74		$951.5023	$951.50	$951.55	$951.50