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	$94.37	9.613%	$103.4418	$103.44	$103.45	$103.40
Purchase #2	$125.97	10.833%	$139.6163	$139.62	$139.60	$139.60
Purchase #3	$129.80	10.367%	$143.2564	$143.26	$143.25	$143.30
Purchase #4	$13.88	13.611%	$15.7692	$15.77	$15.75	$15.80
Purchase #5	$189.56	5.188%	$199.3944	$199.39	$199.40	$199.40
Purchase #6	$90.60	12.690%	$102.0971	$102.10	$102.10	$102.10
Purchase #7	$213.39	7.737%	$229.9	$229.90	$229.90	$229.90
7 purchase totals =	$857.57		$933.4752	$933.48	$933.45	$933.50