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	$223.93	4.165%	$233.2567	$233.26	$233.25	$233.30
Purchase #2	$41.67	4.545%	$43.5639	$43.56	$43.55	$43.60
Purchase #3	$87.54	13.546%	$99.3982	$99.40	$99.40	$99.40
Purchase #4	$158.58	7.105%	$169.8471	$169.85	$169.85	$169.80
Purchase #5	$111.43	9.343%	$121.8409	$121.84	$121.85	$121.80
Purchase #6	$88.43	12.730%	$99.6871	$99.69	$99.70	$99.70
Purchase #7	$183.43	4.453%	$191.5981	$191.60	$191.60	$191.60
7 purchase totals =	$895.01		$959.1920	$959.20	$959.20	$959.20