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	$13.85	5.278%	$14.581	$14.58	$14.60	$14.60
Purchase #2	$161.89	13.587%	$183.886	$183.89	$183.90	$183.90
Purchase #3	$200.46	4.646%	$209.7734	$209.77	$209.75	$209.80
Purchase #4	$248.89	3.805%	$258.3603	$258.36	$258.35	$258.40
Purchase #5	$111.38	4.628%	$116.5347	$116.53	$116.55	$116.50
Purchase #6	$36.89	13.416%	$41.8392	$41.84	$41.85	$41.80
Purchase #7	$111.72	4.264%	$116.4837	$116.48	$116.50	$116.50
7 purchase totals =	$885.08		$941.4583	$941.45	$941.50	$941.50