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	$122.50	4.398%	$127.8876	$127.89	$127.90	$127.90
Purchase #2	$228.38	11.604%	$254.8812	$254.88	$254.90	$254.90
Purchase #3	$114.25	3.220%	$117.9289	$117.93	$117.95	$117.90
Purchase #4	$244.90	4.586%	$256.1311	$256.13	$256.15	$256.10
Purchase #5	$155.80	3.198%	$160.7825	$160.78	$160.80	$160.80
Purchase #6	$207.26	4.646%	$216.8893	$216.89	$216.90	$216.90
Purchase #7	$63.54	13.296%	$71.9883	$71.99	$72.00	$72.00
7 purchase totals =	$1,136.63		$1,206.4889	$1,206.49	$1,206.60	$1,206.50