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	$49.69	13.791%	$56.5427	$56.54	$56.55	$56.50
Purchase #2	$159.85	3.389%	$165.2673	$165.27	$165.25	$165.30
Purchase #3	$95.87	5.790%	$101.4209	$101.42	$101.40	$101.40
Purchase #4	$103.33	10.169%	$113.8376	$113.84	$113.85	$113.80
Purchase #5	$28.66	10.561%	$31.6868	$31.69	$31.70	$31.70
Purchase #6	$227.48	4.792%	$238.3808	$238.38	$238.40	$238.40
Purchase #7	$228.60	5.806%	$241.8725	$241.87	$241.85	$241.90
7 purchase totals =	$893.48		$949.0086	$949.01	$949.00	$949.00