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	$214.60	8.694%	$233.2573	$233.26	$233.25	$233.30
Purchase #2	$230.49	13.594%	$261.8228	$261.82	$261.80	$261.80
Purchase #3	$46.72	10.288%	$51.5266	$51.53	$51.55	$51.50
Purchase #4	$186.64	11.682%	$208.4433	$208.44	$208.45	$208.40
Purchase #5	$63.40	5.506%	$66.8908	$66.89	$66.90	$66.90
Purchase #6	$63.82	11.299%	$71.031	$71.03	$71.05	$71.00
Purchase #7	$6.95	6.407%	$7.3953	$7.40	$7.40	$7.40
7 purchase totals =	$812.62		$900.3671	$900.37	$900.40	$900.30