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	$111.80	10.413%	$123.4417	$123.44	$123.45	$123.40
Purchase #2	$139.87	11.359%	$155.7578	$155.76	$155.75	$155.80
Purchase #3	$54.47	9.183%	$59.472	$59.47	$59.45	$59.50
Purchase #4	$7.92	5.204%	$8.3322	$8.33	$8.35	$8.30
Purchase #5	$178.35	6.720%	$190.3351	$190.34	$190.35	$190.30
Purchase #6	$209.31	7.256%	$224.4975	$224.50	$224.50	$224.50
Purchase #7	$237.37	12.286%	$266.5333	$266.53	$266.55	$266.50
7 purchase totals =	$939.09		$1,028.3696	$1,028.37	$1,028.40	$1,028.30