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	$172.99	10.156%	$190.5589	$190.56	$190.55	$190.60
Purchase #2	$156.78	7.158%	$168.0023	$168.00	$168.00	$168.00
Purchase #3	$45.58	9.327%	$49.8312	$49.83	$49.85	$49.80
Purchase #4	$189.49	12.603%	$213.3714	$213.37	$213.35	$213.40
Purchase #5	$116.73	10.386%	$128.8536	$128.85	$128.85	$128.90
Purchase #6	$103.80	8.381%	$112.4995	$112.50	$112.50	$112.50
Purchase #7	$225.92	3.323%	$233.4273	$233.43	$233.45	$233.40
7 purchase totals =	$1,011.29		$1,096.5442	$1,096.54	$1,096.55	$1,096.60