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	$7.26	11.284%	$8.0792	$8.08	$8.10	$8.10
Purchase #2	$54.53	8.204%	$59.0036	$59.00	$59.00	$59.00
Purchase #3	$40.48	12.633%	$45.5938	$45.59	$45.60	$45.60
Purchase #4	$83.52	10.235%	$92.0683	$92.07	$92.05	$92.10
Purchase #5	$248.45	11.281%	$276.4776	$276.48	$276.50	$276.50
Purchase #6	$215.93	7.464%	$232.047	$232.05	$232.05	$232.00
Purchase #7	$49.89	7.426%	$53.5948	$53.59	$53.60	$53.60
7 purchase totals =	$700.06		$766.8643	$766.86	$766.90	$766.90