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	$57.39	3.301%	$59.2844	$59.28	$59.30	$59.30
Purchase #2	$5.52	4.584%	$5.773	$5.77	$5.75	$5.80
Purchase #3	$164.35	6.117%	$174.4033	$174.40	$174.40	$174.40
Purchase #4	$86.84	10.238%	$95.7307	$95.73	$95.75	$95.70
Purchase #5	$210.49	13.829%	$239.5987	$239.60	$239.60	$239.60
Purchase #6	$45.85	8.188%	$49.6042	$49.60	$49.60	$49.60
Purchase #7	$144.80	12.205%	$162.4728	$162.47	$162.45	$162.50
7 purchase totals =	$715.24		$786.8671	$786.85	$786.85	$786.90