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	$218.95	6.797%	$233.832	$233.83	$233.85	$233.80
Purchase #2	$131.28	7.300%	$140.8634	$140.86	$140.85	$140.90
Purchase #3	$121.89	8.517%	$132.2714	$132.27	$132.25	$132.30
Purchase #4	$178.27	5.168%	$187.483	$187.48	$187.50	$187.50
Purchase #5	$59.84	4.482%	$62.522	$62.52	$62.50	$62.50
Purchase #6	$125.95	6.146%	$133.6909	$133.69	$133.70	$133.70
Purchase #7	$157.56	13.433%	$178.725	$178.73	$178.75	$178.70
7 purchase totals =	$993.74		$1,069.3877	$1,069.38	$1,069.40	$1,069.40