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	$39.90	9.263%	$43.5959	$43.60	$43.60	$43.60
Purchase #2	$95.33	5.610%	$100.678	$100.68	$100.70	$100.70
Purchase #3	$83.57	10.403%	$92.2638	$92.26	$92.25	$92.30
Purchase #4	$68.49	8.747%	$74.4808	$74.48	$74.50	$74.50
Purchase #5	$167.91	5.116%	$176.5003	$176.50	$176.50	$176.50
Purchase #6	$145.91	4.588%	$152.6044	$152.60	$152.60	$152.60
Purchase #7	$169.83	12.442%	$190.9602	$190.96	$190.95	$191.00
7 purchase totals =	$770.94		$831.0834	$831.08	$831.10	$831.20