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	$127.95	12.137%	$143.4793	$143.48	$143.50	$143.50
Purchase #2	$131.82	4.542%	$137.8073	$137.81	$137.80	$137.80
Purchase #3	$211.62	10.816%	$234.5088	$234.51	$234.50	$234.50
Purchase #4	$12.77	9.293%	$13.9567	$13.96	$13.95	$14.00
Purchase #5	$47.27	9.162%	$51.6009	$51.60	$51.60	$51.60
Purchase #6	$236.91	11.264%	$263.5955	$263.60	$263.60	$263.60
Purchase #7	$138.58	4.113%	$144.2798	$144.28	$144.30	$144.30
7 purchase totals =	$906.92		$989.2283	$989.24	$989.25	$989.30