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	$182.85	5.296%	$192.5337	$192.53	$192.55	$192.50
Purchase #2	$92.47	4.624%	$96.7458	$96.75	$96.75	$96.70
Purchase #3	$124.52	11.513%	$138.856	$138.86	$138.85	$138.90
Purchase #4	$31.43	13.774%	$35.7592	$35.76	$35.75	$35.80
Purchase #5	$153.82	12.345%	$172.8091	$172.81	$172.80	$172.80
Purchase #6	$19.50	5.636%	$20.599	$20.60	$20.60	$20.60
Purchase #7	$45.50	7.374%	$48.8552	$48.86	$48.85	$48.90
7 purchase totals =	$650.09		$706.1580	$706.17	$706.15	$706.20