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	$89.96	11.752%	$100.5321	$100.53	$100.55	$100.50
Purchase #2	$125.95	4.599%	$131.7424	$131.74	$131.75	$131.70
Purchase #3	$35.85	7.105%	$38.3971	$38.40	$38.40	$38.40
Purchase #4	$140.45	10.249%	$154.8447	$154.84	$154.85	$154.80
Purchase #5	$211.38	13.611%	$240.1509	$240.15	$240.15	$240.20
Purchase #6	$41.37	11.282%	$46.0374	$46.04	$46.05	$46.00
Purchase #7	$87.48	5.145%	$91.9808	$91.98	$92.00	$92.00
7 purchase totals =	$732.44		$803.6854	$803.68	$803.75	$803.60