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	$200.38	8.479%	$217.3702	$217.37	$217.35	$217.40
Purchase #2	$50.89	5.519%	$53.6986	$53.70	$53.70	$53.70
Purchase #3	$13.75	8.388%	$14.9034	$14.90	$14.90	$14.90
Purchase #4	$137.98	10.513%	$152.4858	$152.49	$152.50	$152.50
Purchase #5	$249.62	12.487%	$280.79	$280.79	$280.80	$280.80
Purchase #6	$40.54	12.278%	$45.5175	$45.52	$45.50	$45.50
Purchase #7	$48.72	8.332%	$52.7794	$52.78	$52.80	$52.80
7 purchase totals =	$741.88		$817.5449	$817.55	$817.55	$817.60