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	$54.91	13.798%	$62.4865	$62.49	$62.50	$62.50
Purchase #2	$10.69	11.535%	$11.9231	$11.92	$11.90	$11.90
Purchase #3	$60.72	4.581%	$63.5016	$63.50	$63.50	$63.50
Purchase #4	$64.72	10.472%	$71.4975	$71.50	$71.50	$71.50
Purchase #5	$198.45	8.810%	$215.9334	$215.93	$215.95	$215.90
Purchase #6	$112.37	13.262%	$127.2725	$127.27	$127.25	$127.30
Purchase #7	$157.92	9.815%	$173.4198	$173.42	$173.40	$173.40
7 purchase totals =	$659.78		$726.0344	$726.03	$726.00	$726.00