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	$151.93	13.585%	$172.5697	$172.57	$172.55	$172.60
Purchase #2	$169.48	10.320%	$186.9703	$186.97	$186.95	$187.00
Purchase #3	$58.60	5.429%	$61.7814	$61.78	$61.80	$61.80
Purchase #4	$120.72	6.460%	$128.5185	$128.52	$128.50	$128.50
Purchase #5	$141.43	13.855%	$161.0251	$161.03	$161.05	$161.00
Purchase #6	$97.81	13.776%	$111.2843	$111.28	$111.30	$111.30
Purchase #7	$61.45	7.491%	$66.0532	$66.05	$66.05	$66.10
7 purchase totals =	$801.42		$888.2025	$888.20	$888.20	$888.30