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	$61.61	11.677%	$68.8042	$68.80	$68.80	$68.80
Purchase #2	$130.55	11.759%	$145.9014	$145.90	$145.90	$145.90
Purchase #3	$108.39	9.210%	$118.3727	$118.37	$118.35	$118.40
Purchase #4	$161.58	3.664%	$167.5003	$167.50	$167.50	$167.50
Purchase #5	$111.46	4.564%	$116.547	$116.55	$116.55	$116.50
Purchase #6	$128.77	8.225%	$139.3613	$139.36	$139.35	$139.40
Purchase #7	$60.51	5.783%	$64.0093	$64.01	$64.00	$64.00
7 purchase totals =	$762.87		$820.4962	$820.49	$820.45	$820.50