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	$53.42	3.838%	$55.4703	$55.47	$55.45	$55.50
Purchase #2	$123.66	6.445%	$131.6299	$131.63	$131.65	$131.60
Purchase #3	$38.39	6.254%	$40.7909	$40.79	$40.80	$40.80
Purchase #4	$66.48	9.678%	$72.9139	$72.91	$72.90	$72.90
Purchase #5	$200.67	13.517%	$227.7946	$227.79	$227.80	$227.80
Purchase #6	$95.68	11.517%	$106.6995	$106.70	$106.70	$106.70
Purchase #7	$185.29	13.859%	$210.9693	$210.97	$210.95	$211.00
7 purchase totals =	$763.59		$846.2684	$846.26	$846.25	$846.30