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	$5.44	7.864%	$5.8678	$5.87	$5.85	$5.90
Purchase #2	$76.88	7.759%	$82.8451	$82.85	$82.85	$82.80
Purchase #3	$169.72	11.561%	$189.3413	$189.34	$189.35	$189.30
Purchase #4	$244.26	10.471%	$269.8365	$269.84	$269.85	$269.80
Purchase #5	$168.62	4.746%	$176.6227	$176.62	$176.60	$176.60
Purchase #6	$224.47	13.832%	$255.5187	$255.52	$255.50	$255.50
Purchase #7	$50.50	8.576%	$54.8309	$54.83	$54.85	$54.80
7 purchase totals =	$939.89		$1,034.8630	$1,034.87	$1,034.85	$1,034.70