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	$162.52	5.128%	$170.854	$170.85	$170.85	$170.90
Purchase #2	$197.26	9.144%	$215.2975	$215.30	$215.30	$215.30
Purchase #3	$216.78	12.667%	$244.2395	$244.24	$244.25	$244.20
Purchase #4	$19.60	9.725%	$21.5061	$21.51	$21.50	$21.50
Purchase #5	$72.54	5.366%	$76.4325	$76.43	$76.45	$76.40
Purchase #6	$99.32	3.300%	$102.5976	$102.60	$102.60	$102.60
Purchase #7	$116.57	3.732%	$120.9204	$120.92	$120.90	$120.90
7 purchase totals =	$884.59		$951.8476	$951.85	$951.85	$951.80