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	$61.49	6.569%	$65.5293	$65.53	$65.55	$65.50
Purchase #2	$30.75	7.429%	$33.0344	$33.03	$33.05	$33.00
Purchase #3	$242.89	5.559%	$256.3923	$256.39	$256.40	$256.40
Purchase #4	$46.39	6.695%	$49.4958	$49.50	$49.50	$49.50
Purchase #5	$159.63	6.213%	$169.5478	$169.55	$169.55	$169.50
Purchase #6	$149.56	4.255%	$155.9238	$155.92	$155.90	$155.90
Purchase #7	$139.57	8.632%	$151.6177	$151.62	$151.60	$151.60
7 purchase totals =	$830.28		$881.5411	$881.54	$881.55	$881.40