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	$225.93	3.456%	$233.7381	$233.74	$233.75	$233.70
Purchase #2	$226.53	4.233%	$236.119	$236.12	$236.10	$236.10
Purchase #3	$199.88	3.608%	$207.0917	$207.09	$207.10	$207.10
Purchase #4	$134.52	7.702%	$144.8807	$144.88	$144.90	$144.90
Purchase #5	$248.87	11.807%	$278.2541	$278.25	$278.25	$278.30
Purchase #6	$102.50	9.171%	$111.9003	$111.90	$111.90	$111.90
Purchase #7	$73.99	6.548%	$78.8349	$78.83	$78.85	$78.80
7 purchase totals =	$1,212.22		$1,290.8188	$1,290.81	$1,290.85	$1,290.80