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	$127.59	12.523%	$143.5681	$143.57	$143.55	$143.60
Purchase #2	$248.82	13.426%	$282.2266	$282.23	$282.25	$282.20
Purchase #3	$124.35	3.572%	$128.7918	$128.79	$128.80	$128.80
Purchase #4	$10.96	8.740%	$11.9179	$11.92	$11.90	$11.90
Purchase #5	$215.58	9.853%	$236.8211	$236.82	$236.80	$236.80
Purchase #6	$19.98	7.360%	$21.4505	$21.45	$21.45	$21.50
Purchase #7	$181.94	5.596%	$192.1214	$192.12	$192.10	$192.10
7 purchase totals =	$929.22		$1,016.8974	$1,016.90	$1,016.85	$1,016.90