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	$233.98	4.104%	$243.5825	$243.58	$243.60	$243.60
Purchase #2	$125.52	5.364%	$132.2529	$132.25	$132.25	$132.30
Purchase #3	$107.79	6.204%	$114.4773	$114.48	$114.50	$114.50
Purchase #4	$119.71	3.211%	$123.5539	$123.55	$123.55	$123.60
Purchase #5	$213.72	12.586%	$240.6188	$240.62	$240.60	$240.60
Purchase #6	$76.88	8.151%	$83.1465	$83.15	$83.15	$83.10
Purchase #7	$225.61	13.192%	$255.3725	$255.37	$255.35	$255.40
7 purchase totals =	$1,103.21		$1,193.0044	$1,193.00	$1,193.00	$1,193.10