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	$197.97	13.447%	$224.591	$224.59	$224.60	$224.60
Purchase #2	$195.50	4.246%	$203.8009	$203.80	$203.80	$203.80
Purchase #3	$81.81	6.531%	$87.153	$87.15	$87.15	$87.20
Purchase #4	$215.74	8.246%	$233.5299	$233.53	$233.55	$233.50
Purchase #5	$81.46	6.203%	$86.513	$86.51	$86.50	$86.50
Purchase #6	$247.77	13.222%	$280.5301	$280.53	$280.55	$280.50
Purchase #7	$65.27	10.832%	$72.34	$72.34	$72.35	$72.30
7 purchase totals =	$1,085.52		$1,188.4579	$1,188.45	$1,188.50	$1,188.40