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	$165.90	9.338%	$181.3917	$181.39	$181.40	$181.40
Purchase #2	$86.97	9.581%	$95.3026	$95.30	$95.30	$95.30
Purchase #3	$91.45	3.202%	$94.3782	$94.38	$94.40	$94.40
Purchase #4	$122.53	8.142%	$132.5064	$132.51	$132.50	$132.50
Purchase #5	$45.97	13.441%	$52.1488	$52.15	$52.15	$52.10
Purchase #6	$130.79	7.835%	$141.0374	$141.04	$141.05	$141.00
Purchase #7	$142.98	11.801%	$159.8531	$159.85	$159.85	$159.90
7 purchase totals =	$786.59		$856.6182	$856.62	$856.65	$856.60