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	$69.90	9.467%	$76.5174	$76.52	$76.50	$76.50
Purchase #2	$41.48	10.857%	$45.9835	$45.98	$46.00	$46.00
Purchase #3	$126.60	3.792%	$131.4007	$131.40	$131.40	$131.40
Purchase #4	$46.50	11.398%	$51.8001	$51.80	$51.80	$51.80
Purchase #5	$146.92	10.856%	$162.8696	$162.87	$162.85	$162.90
Purchase #6	$75.80	13.473%	$86.0125	$86.01	$86.00	$86.00
Purchase #7	$9.61	13.718%	$10.9283	$10.93	$10.95	$10.90
7 purchase totals =	$516.81		$565.5121	$565.51	$565.50	$565.50