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	$167.72	13.796%	$190.8587	$190.86	$190.85	$190.90
Purchase #2	$105.29	5.667%	$111.2568	$111.26	$111.25	$111.30
Purchase #3	$123.78	11.554%	$138.0815	$138.08	$138.10	$138.10
Purchase #4	$107.34	13.259%	$121.5722	$121.57	$121.55	$121.60
Purchase #5	$50.95	13.665%	$57.9123	$57.91	$57.90	$57.90
Purchase #6	$115.72	13.848%	$131.7449	$131.74	$131.75	$131.70
Purchase #7	$112.47	6.228%	$119.4746	$119.47	$119.45	$119.50
7 purchase totals =	$783.27		$870.9010	$870.89	$870.85	$871.00