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	$6.81	8.748%	$7.4057	$7.41	$7.40	$7.40
Purchase #2	$10.85	10.153%	$11.9516	$11.95	$11.95	$12.00
Purchase #3	$38.79	10.394%	$42.8218	$42.82	$42.80	$42.80
Purchase #4	$235.25	10.762%	$260.5676	$260.57	$260.55	$260.60
Purchase #5	$25.88	7.759%	$27.888	$27.89	$27.90	$27.90
Purchase #6	$186.52	13.566%	$211.8233	$211.82	$211.80	$211.80
Purchase #7	$59.46	4.352%	$62.0477	$62.05	$62.05	$62.00
7 purchase totals =	$563.56		$624.5057	$624.51	$624.45	$624.50