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	$131.86	11.766%	$147.3746	$147.37	$147.35	$147.40
Purchase #2	$47.35	5.204%	$49.8141	$49.81	$49.80	$49.80
Purchase #3	$42.77	7.296%	$45.8905	$45.89	$45.90	$45.90
Purchase #4	$10.58	11.542%	$11.8011	$11.80	$11.80	$11.80
Purchase #5	$64.86	12.338%	$72.8624	$72.86	$72.85	$72.90
Purchase #6	$69.97	8.699%	$76.0567	$76.06	$76.05	$76.10
Purchase #7	$145.65	7.268%	$156.2358	$156.24	$156.25	$156.20
7 purchase totals =	$513.04		$560.0352	$560.03	$560.00	$560.10