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	$96.46	10.744%	$106.8237	$106.82	$106.80	$106.80
Purchase #2	$27.82	13.119%	$31.4697	$31.47	$31.45	$31.50
Purchase #3	$120.49	8.793%	$131.0847	$131.08	$131.10	$131.10
Purchase #4	$172.39	11.725%	$192.6027	$192.60	$192.60	$192.60
Purchase #5	$210.52	5.682%	$222.4817	$222.48	$222.50	$222.50
Purchase #6	$54.66	10.412%	$60.3512	$60.35	$60.35	$60.40
Purchase #7	$84.92	4.321%	$88.5894	$88.59	$88.60	$88.60
7 purchase totals =	$767.26		$833.4031	$833.39	$833.40	$833.50