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	$126.87	11.549%	$141.5222	$141.52	$141.50	$141.50
Purchase #2	$73.45	12.772%	$82.831	$82.83	$82.85	$82.80
Purchase #3	$202.96	6.292%	$215.7302	$215.73	$215.75	$215.70
Purchase #4	$19.46	7.734%	$20.965	$20.97	$20.95	$21.00
Purchase #5	$196.69	9.383%	$215.1454	$215.15	$215.15	$215.10
Purchase #6	$47.74	9.679%	$52.3608	$52.36	$52.35	$52.40
Purchase #7	$209.50	8.742%	$227.8145	$227.81	$227.80	$227.80
7 purchase totals =	$876.67		$956.3691	$956.37	$956.35	$956.30