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	$15.27	7.782%	$16.4583	$16.46	$16.45	$16.50
Purchase #2	$50.60	11.839%	$56.5905	$56.59	$56.60	$56.60
Purchase #3	$127.28	5.245%	$133.9558	$133.96	$133.95	$134.00
Purchase #4	$119.97	8.696%	$130.4026	$130.40	$130.40	$130.40
Purchase #5	$172.55	10.139%	$190.0448	$190.04	$190.05	$190.00
Purchase #6	$155.27	8.324%	$168.1947	$168.19	$168.20	$168.20
Purchase #7	$142.89	5.482%	$150.7232	$150.72	$150.70	$150.70
7 purchase totals =	$783.83		$846.3699	$846.36	$846.35	$846.40