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	$191.91	9.351%	$209.8555	$209.86	$209.85	$209.90
Purchase #2	$179.71	11.177%	$199.7962	$199.80	$199.80	$199.80
Purchase #3	$23.67	12.125%	$26.54	$26.54	$26.55	$26.50
Purchase #4	$81.96	10.393%	$90.4781	$90.48	$90.50	$90.50
Purchase #5	$216.65	6.823%	$231.432	$231.43	$231.45	$231.40
Purchase #6	$127.29	9.531%	$139.422	$139.42	$139.40	$139.40
Purchase #7	$137.50	3.642%	$142.5078	$142.51	$142.50	$142.50
7 purchase totals =	$958.69		$1,040.0316	$1,040.04	$1,040.05	$1,040.00