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	$83.48	4.246%	$87.0246	$87.02	$87.00	$87.00
Purchase #2	$131.58	6.479%	$140.1051	$140.11	$140.10	$140.10
Purchase #3	$59.96	4.704%	$62.7805	$62.78	$62.80	$62.80
Purchase #4	$62.55	4.587%	$65.4192	$65.42	$65.40	$65.40
Purchase #5	$205.85	5.333%	$216.828	$216.83	$216.85	$216.80
Purchase #6	$72.68	6.266%	$77.2341	$77.23	$77.25	$77.20
Purchase #7	$140.61	11.401%	$156.6409	$156.64	$156.65	$156.60
7 purchase totals =	$756.71		$806.0324	$806.03	$806.05	$805.90