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	$64.66	9.286%	$70.6643	$70.66	$70.65	$70.70
Purchase #2	$40.94	11.175%	$45.515	$45.52	$45.50	$45.50
Purchase #3	$58.60	7.261%	$62.8549	$62.85	$62.85	$62.90
Purchase #4	$64.70	10.614%	$71.5673	$71.57	$71.55	$71.60
Purchase #5	$102.81	8.717%	$111.7719	$111.77	$111.75	$111.80
Purchase #6	$191.38	4.757%	$200.4839	$200.48	$200.50	$200.50
Purchase #7	$132.62	8.549%	$143.9577	$143.96	$143.95	$144.00
7 purchase totals =	$655.71		$706.8150	$706.81	$706.75	$707.00