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	$205.34	5.171%	$215.9581	$215.96	$215.95	$216.00
Purchase #2	$98.46	13.857%	$112.1036	$112.10	$112.10	$112.10
Purchase #3	$71.58	5.722%	$75.6758	$75.68	$75.70	$75.70
Purchase #4	$158.45	12.719%	$178.6033	$178.60	$178.60	$178.60
Purchase #5	$87.47	3.832%	$90.8219	$90.82	$90.80	$90.80
Purchase #6	$121.81	6.330%	$129.5206	$129.52	$129.50	$129.50
Purchase #7	$70.81	11.451%	$78.9185	$78.92	$78.90	$78.90
7 purchase totals =	$813.92		$881.6018	$881.60	$881.55	$881.60