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	$59.76	6.815%	$63.8326	$63.83	$63.85	$63.80
Purchase #2	$9.41	6.736%	$10.0439	$10.04	$10.05	$10.00
Purchase #3	$77.60	6.220%	$82.4267	$82.43	$82.45	$82.40
Purchase #4	$127.73	11.871%	$142.8928	$142.89	$142.90	$142.90
Purchase #5	$96.27	6.462%	$102.491	$102.49	$102.50	$102.50
Purchase #6	$9.77	6.814%	$10.4357	$10.44	$10.45	$10.40
Purchase #7	$162.55	4.595%	$170.0192	$170.02	$170.00	$170.00
7 purchase totals =	$543.09		$582.1419	$582.14	$582.20	$582.00