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	$40.87	6.106%	$43.3655	$43.37	$43.35	$43.40
Purchase #2	$238.67	9.349%	$260.9833	$260.98	$261.00	$261.00
Purchase #3	$180.75	5.306%	$190.3406	$190.34	$190.35	$190.30
Purchase #4	$212.81	12.120%	$238.6026	$238.60	$238.60	$238.60
Purchase #5	$111.61	5.248%	$117.4673	$117.47	$117.45	$117.50
Purchase #6	$160.60	6.476%	$171.0005	$171.00	$171.00	$171.00
Purchase #7	$144.28	4.239%	$150.396	$150.40	$150.40	$150.40
7 purchase totals =	$1,089.59		$1,172.1558	$1,172.16	$1,172.15	$1,172.20