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	$150.80	12.610%	$169.8159	$169.82	$169.80	$169.80
Purchase #2	$56.25	10.551%	$62.1849	$62.18	$62.20	$62.20
Purchase #3	$244.41	5.168%	$257.0411	$257.04	$257.05	$257.00
Purchase #4	$183.53	13.711%	$208.6938	$208.69	$208.70	$208.70
Purchase #5	$173.56	9.483%	$190.0187	$190.02	$190.00	$190.00
Purchase #6	$77.81	13.696%	$88.4669	$88.47	$88.45	$88.50
Purchase #7	$139.54	11.395%	$155.4406	$155.44	$155.45	$155.40
7 purchase totals =	$1,025.90		$1,131.6619	$1,131.66	$1,131.65	$1,131.60