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	$37.45	12.493%	$42.1286	$42.13	$42.15	$42.10
Purchase #2	$217.42	3.144%	$224.2557	$224.26	$224.25	$224.30
Purchase #3	$143.83	8.866%	$156.582	$156.58	$156.60	$156.60
Purchase #4	$153.54	11.145%	$170.652	$170.65	$170.65	$170.70
Purchase #5	$84.81	6.594%	$90.4024	$90.40	$90.40	$90.40
Purchase #6	$232.85	9.540%	$255.0639	$255.06	$255.05	$255.10
Purchase #7	$236.82	10.416%	$261.4872	$261.49	$261.50	$261.50
7 purchase totals =	$1,106.72		$1,200.5718	$1,200.57	$1,200.60	$1,200.70