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	$113.78	12.130%	$127.5815	$127.58	$127.60	$127.60
Purchase #2	$181.47	5.583%	$191.6015	$191.60	$191.60	$191.60
Purchase #3	$7.97	6.770%	$8.5096	$8.51	$8.50	$8.50
Purchase #4	$97.96	3.185%	$101.08	$101.08	$101.10	$101.10
Purchase #5	$250.60	4.610%	$262.1527	$262.15	$262.15	$262.20
Purchase #6	$13.78	10.802%	$15.2685	$15.27	$15.25	$15.30
Purchase #7	$202.57	12.140%	$227.162	$227.16	$227.15	$227.20
7 purchase totals =	$868.13		$933.3558	$933.35	$933.35	$933.50