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	$180.52	8.782%	$196.3733	$196.37	$196.35	$196.40
Purchase #2	$132.94	5.204%	$139.8582	$139.86	$139.85	$139.90
Purchase #3	$137.41	3.613%	$142.3746	$142.37	$142.35	$142.40
Purchase #4	$191.56	8.584%	$208.0035	$208.00	$208.00	$208.00
Purchase #5	$102.62	6.407%	$109.1949	$109.19	$109.20	$109.20
Purchase #6	$62.83	8.659%	$68.2704	$68.27	$68.25	$68.30
Purchase #7	$38.48	8.364%	$41.6985	$41.70	$41.70	$41.70
7 purchase totals =	$846.36		$905.7734	$905.76	$905.70	$905.90