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	$91.55	7.516%	$98.4309	$98.43	$98.45	$98.40
Purchase #2	$12.88	4.739%	$13.4904	$13.49	$13.50	$13.50
Purchase #3	$118.93	10.189%	$131.0478	$131.05	$131.05	$131.00
Purchase #4	$131.89	7.608%	$141.9242	$141.92	$141.90	$141.90
Purchase #5	$19.27	5.174%	$20.267	$20.27	$20.25	$20.30
Purchase #6	$180.26	4.379%	$188.1536	$188.15	$188.15	$188.20
Purchase #7	$187.25	12.713%	$211.0551	$211.06	$211.05	$211.10
7 purchase totals =	$742.03		$804.3690	$804.37	$804.35	$804.40