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	$78.81	10.647%	$87.2009	$87.20	$87.20	$87.20
Purchase #2	$172.53	13.659%	$196.0959	$196.10	$196.10	$196.10
Purchase #3	$151.60	12.108%	$169.9557	$169.96	$169.95	$170.00
Purchase #4	$108.98	4.424%	$113.8013	$113.80	$113.80	$113.80
Purchase #5	$110.40	12.139%	$123.8015	$123.80	$123.80	$123.80
Purchase #6	$189.86	13.333%	$215.174	$215.17	$215.15	$215.20
Purchase #7	$36.71	13.838%	$41.7899	$41.79	$41.80	$41.80
7 purchase totals =	$848.89		$947.8192	$947.82	$947.80	$947.90