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	$117.84	5.837%	$124.7183	$124.72	$124.70	$124.70
Purchase #2	$235.47	7.269%	$252.5863	$252.59	$252.60	$252.60
Purchase #3	$222.45	7.305%	$238.7	$238.70	$238.70	$238.70
Purchase #4	$146.65	9.395%	$160.4278	$160.43	$160.45	$160.40
Purchase #5	$84.60	5.252%	$89.0432	$89.04	$89.05	$89.00
Purchase #6	$34.89	7.569%	$37.5308	$37.53	$37.55	$37.50
Purchase #7	$57.56	10.489%	$63.5975	$63.60	$63.60	$63.60
7 purchase totals =	$899.46		$966.6039	$966.61	$966.65	$966.50