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	$243.70	10.384%	$269.0058	$269.01	$269.00	$269.00
Purchase #2	$194.82	9.188%	$212.7201	$212.72	$212.70	$212.70
Purchase #3	$100.45	11.254%	$111.7546	$111.75	$111.75	$111.80
Purchase #4	$101.27	4.600%	$105.9284	$105.93	$105.95	$105.90
Purchase #5	$76.72	12.161%	$86.0499	$86.05	$86.05	$86.00
Purchase #6	$134.93	10.421%	$148.9911	$148.99	$149.00	$149.00
Purchase #7	$138.95	9.776%	$152.5338	$152.53	$152.55	$152.50
7 purchase totals =	$990.84		$1,086.9837	$1,086.98	$1,087.00	$1,086.90