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	$241.61	10.778%	$267.6507	$267.65	$267.65	$267.70
Purchase #2	$63.83	6.407%	$67.9196	$67.92	$67.90	$67.90
Purchase #3	$153.82	9.558%	$168.5221	$168.52	$168.50	$168.50
Purchase #4	$132.29	4.662%	$138.4574	$138.46	$138.45	$138.50
Purchase #5	$101.98	10.722%	$112.9143	$112.91	$112.90	$112.90
Purchase #6	$47.48	13.186%	$53.7407	$53.74	$53.75	$53.70
Purchase #7	$123.67	6.436%	$131.6294	$131.63	$131.65	$131.60
7 purchase totals =	$864.68		$940.8342	$940.83	$940.80	$940.80