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	$116.87	12.407%	$131.3701	$131.37	$131.35	$131.40
Purchase #2	$46.67	9.292%	$51.0066	$51.01	$51.00	$51.00
Purchase #3	$115.86	5.566%	$122.3088	$122.31	$122.30	$122.30
Purchase #4	$140.26	4.421%	$146.4609	$146.46	$146.45	$146.50
Purchase #5	$31.52	6.179%	$33.4676	$33.47	$33.45	$33.50
Purchase #6	$192.92	12.219%	$216.4929	$216.49	$216.50	$216.50
Purchase #7	$85.67	11.381%	$95.4201	$95.42	$95.40	$95.40
7 purchase totals =	$729.77		$796.5270	$796.53	$796.45	$796.60