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	$150.83	9.770%	$165.5661	$165.57	$165.55	$165.60
Purchase #2	$64.42	12.725%	$72.6174	$72.62	$72.60	$72.60
Purchase #3	$72.96	6.726%	$77.8673	$77.87	$77.85	$77.90
Purchase #4	$173.66	10.581%	$192.035	$192.04	$192.05	$192.00
Purchase #5	$30.35	3.419%	$31.3877	$31.39	$31.40	$31.40
Purchase #6	$166.65	3.536%	$172.5427	$172.54	$172.55	$172.50
Purchase #7	$91.66	8.821%	$99.7453	$99.75	$99.75	$99.70
7 purchase totals =	$750.53		$811.7615	$811.78	$811.75	$811.70