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	$207.35	3.724%	$215.0717	$215.07	$215.05	$215.10
Purchase #2	$136.55	5.166%	$143.6042	$143.60	$143.60	$143.60
Purchase #3	$124.29	12.139%	$139.3776	$139.38	$139.40	$139.40
Purchase #4	$86.64	11.494%	$96.5984	$96.60	$96.60	$96.60
Purchase #5	$244.69	3.863%	$254.1424	$254.14	$254.15	$254.10
Purchase #6	$233.50	9.431%	$255.5214	$255.52	$255.50	$255.50
Purchase #7	$157.79	12.758%	$177.9208	$177.92	$177.90	$177.90
7 purchase totals =	$1,190.81		$1,282.2365	$1,282.23	$1,282.20	$1,282.20