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	$38.87	12.735%	$43.8201	$43.82	$43.80	$43.80
Purchase #2	$100.26	9.427%	$109.7115	$109.71	$109.70	$109.70
Purchase #3	$225.78	3.307%	$233.2465	$233.25	$233.25	$233.20
Purchase #4	$34.95	6.550%	$37.2392	$37.24	$37.25	$37.20
Purchase #5	$187.95	11.633%	$209.8142	$209.81	$209.80	$209.80
Purchase #6	$108.80	3.823%	$112.9594	$112.96	$112.95	$113.00
Purchase #7	$209.66	8.389%	$227.2484	$227.25	$227.25	$227.20
7 purchase totals =	$906.27		$974.0393	$974.04	$974.00	$973.90