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	$94.64	7.257%	$101.508	$101.51	$101.50	$101.50
Purchase #2	$43.50	11.666%	$48.5747	$48.57	$48.55	$48.60
Purchase #3	$41.57	8.612%	$45.15	$45.15	$45.15	$45.20
Purchase #4	$167.50	5.213%	$176.2318	$176.23	$176.25	$176.20
Purchase #5	$247.60	11.794%	$276.8019	$276.80	$276.80	$276.80
Purchase #6	$203.89	12.856%	$230.1021	$230.10	$230.10	$230.10
Purchase #7	$87.59	5.555%	$92.4556	$92.46	$92.45	$92.50
7 purchase totals =	$886.29		$970.8241	$970.82	$970.80	$970.90