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	$105.80	5.779%	$111.9142	$111.91	$111.90	$111.90
Purchase #2	$193.32	10.317%	$213.2648	$213.26	$213.25	$213.30
Purchase #3	$243.60	10.789%	$269.882	$269.88	$269.90	$269.90
Purchase #4	$181.58	4.856%	$190.3975	$190.40	$190.40	$190.40
Purchase #5	$35.98	13.605%	$40.8751	$40.88	$40.90	$40.90
Purchase #6	$131.90	12.812%	$148.799	$148.80	$148.80	$148.80
Purchase #7	$241.48	6.426%	$256.9975	$257.00	$257.00	$257.00
7 purchase totals =	$1,133.66		$1,232.1301	$1,232.13	$1,232.15	$1,232.20