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	$91.70	13.181%	$103.787	$103.79	$103.80	$103.80
Purchase #2	$126.57	9.611%	$138.7346	$138.73	$138.75	$138.70
Purchase #3	$199.59	13.660%	$226.854	$226.85	$226.85	$226.90
Purchase #4	$137.60	3.589%	$142.5385	$142.54	$142.55	$142.50
Purchase #5	$243.70	12.862%	$275.0447	$275.04	$275.05	$275.00
Purchase #6	$111.92	10.340%	$123.4925	$123.49	$123.50	$123.50
Purchase #7	$146.87	5.207%	$154.5175	$154.52	$154.50	$154.50
7 purchase totals =	$1,057.95		$1,164.9688	$1,164.96	$1,165.00	$1,164.90