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	$123.41	7.521%	$132.6917	$132.69	$132.70	$132.70
Purchase #2	$83.74	4.577%	$87.5728	$87.57	$87.55	$87.60
Purchase #3	$137.75	10.785%	$152.6063	$152.61	$152.60	$152.60
Purchase #4	$210.85	5.409%	$222.2549	$222.25	$222.25	$222.30
Purchase #5	$116.34	13.218%	$131.7178	$131.72	$131.70	$131.70
Purchase #6	$144.27	8.623%	$156.7104	$156.71	$156.70	$156.70
Purchase #7	$190.34	13.174%	$215.4154	$215.42	$215.40	$215.40
7 purchase totals =	$1,006.70		$1,098.9693	$1,098.97	$1,098.90	$1,099.00