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	$103.72	9.751%	$113.8337	$113.83	$113.85	$113.80
Purchase #2	$89.86	6.660%	$95.8447	$95.84	$95.85	$95.80
Purchase #3	$67.49	13.661%	$76.7098	$76.71	$76.70	$76.70
Purchase #4	$75.95	12.485%	$85.4324	$85.43	$85.45	$85.40
Purchase #5	$92.83	13.367%	$105.2386	$105.24	$105.25	$105.20
Purchase #6	$31.52	4.809%	$33.0358	$33.04	$33.05	$33.00
Purchase #7	$205.78	12.464%	$231.4284	$231.43	$231.45	$231.40
7 purchase totals =	$667.15		$741.5234	$741.52	$741.60	$741.30