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	$114.40	11.384%	$127.4233	$127.42	$127.40	$127.40
Purchase #2	$174.40	12.156%	$195.6001	$195.60	$195.60	$195.60
Purchase #3	$148.49	6.703%	$158.4433	$158.44	$158.45	$158.40
Purchase #4	$85.59	5.717%	$90.4832	$90.48	$90.50	$90.50
Purchase #5	$17.78	6.140%	$18.8717	$18.87	$18.85	$18.90
Purchase #6	$143.67	13.379%	$162.8916	$162.89	$162.90	$162.90
Purchase #7	$101.85	8.355%	$110.3596	$110.36	$110.35	$110.40
7 purchase totals =	$786.18		$864.0728	$864.06	$864.05	$864.10