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	$100.74	3.762%	$104.5298	$104.53	$104.55	$104.50
Purchase #2	$151.96	13.287%	$172.1509	$172.15	$172.15	$172.20
Purchase #3	$8.61	10.365%	$9.5024	$9.50	$9.50	$9.50
Purchase #4	$235.89	8.120%	$255.0443	$255.04	$255.05	$255.00
Purchase #5	$149.82	13.752%	$170.4232	$170.42	$170.40	$170.40
Purchase #6	$250.98	11.837%	$280.6885	$280.69	$280.70	$280.70
Purchase #7	$174.53	3.129%	$179.991	$179.99	$180.00	$180.00
7 purchase totals =	$1,072.53		$1,172.3301	$1,172.32	$1,172.35	$1,172.30