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	$40.87	7.508%	$43.9385	$43.94	$43.95	$43.90
Purchase #2	$112.85	13.623%	$128.2236	$128.22	$128.20	$128.20
Purchase #3	$175.47	8.540%	$190.4551	$190.46	$190.45	$190.50
Purchase #4	$51.33	4.383%	$53.5798	$53.58	$53.60	$53.60
Purchase #5	$162.82	13.366%	$184.5825	$184.58	$184.60	$184.60
Purchase #6	$66.52	3.109%	$68.5881	$68.59	$68.60	$68.60
Purchase #7	$118.56	5.160%	$124.6777	$124.68	$124.70	$124.70
7 purchase totals =	$728.42		$794.0453	$794.05	$794.10	$794.10