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	$84.90	10.659%	$93.9495	$93.95	$93.95	$93.90
Purchase #2	$79.95	12.618%	$90.0381	$90.04	$90.05	$90.00
Purchase #3	$209.71	7.143%	$224.6896	$224.69	$224.70	$224.70
Purchase #4	$51.91	4.542%	$54.2678	$54.27	$54.25	$54.30
Purchase #5	$94.48	6.745%	$100.8527	$100.85	$100.85	$100.90
Purchase #6	$120.77	11.287%	$134.4013	$134.40	$134.40	$134.40
Purchase #7	$199.78	11.455%	$222.6648	$222.66	$222.65	$222.70
7 purchase totals =	$841.50		$920.8638	$920.86	$920.85	$920.90