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	$75.34	10.131%	$82.9727	$82.97	$82.95	$83.00
Purchase #2	$13.28	4.201%	$13.8379	$13.84	$13.85	$13.80
Purchase #3	$10.87	10.691%	$12.0321	$12.03	$12.05	$12.00
Purchase #4	$248.47	13.701%	$282.5129	$282.51	$282.50	$282.50
Purchase #5	$219.39	5.359%	$231.1471	$231.15	$231.15	$231.10
Purchase #6	$52.80	12.712%	$59.5119	$59.51	$59.50	$59.50
Purchase #7	$81.70	3.534%	$84.5873	$84.59	$84.60	$84.60
7 purchase totals =	$701.85		$766.6019	$766.60	$766.60	$766.50