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	$220.53	10.556%	$243.8091	$243.81	$243.80	$243.80
Purchase #2	$94.78	6.419%	$100.8639	$100.86	$100.85	$100.90
Purchase #3	$153.39	9.564%	$168.0602	$168.06	$168.05	$168.10
Purchase #4	$61.83	6.269%	$65.7061	$65.71	$65.70	$65.70
Purchase #5	$43.87	8.433%	$47.5696	$47.57	$47.55	$47.60
Purchase #6	$73.60	11.328%	$81.9374	$81.94	$81.95	$81.90
Purchase #7	$244.38	10.799%	$270.7706	$270.77	$270.75	$270.80
7 purchase totals =	$892.38		$978.7169	$978.72	$978.65	$978.80