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	$213.46	6.781%	$227.9347	$227.93	$227.95	$227.90
Purchase #2	$68.28	3.189%	$70.4574	$70.46	$70.45	$70.50
Purchase #3	$194.60	3.236%	$200.8973	$200.90	$200.90	$200.90
Purchase #4	$86.47	3.742%	$89.7057	$89.71	$89.70	$89.70
Purchase #5	$127.85	8.330%	$138.4999	$138.50	$138.50	$138.50
Purchase #6	$105.80	13.278%	$119.8481	$119.85	$119.85	$119.80
Purchase #7	$55.82	4.840%	$58.5217	$58.52	$58.50	$58.50
7 purchase totals =	$852.28		$905.8648	$905.87	$905.85	$905.80