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	$70.28	3.313%	$72.6084	$72.61	$72.60	$72.60
Purchase #2	$68.78	13.536%	$78.0901	$78.09	$78.10	$78.10
Purchase #3	$239.97	7.260%	$257.3918	$257.39	$257.40	$257.40
Purchase #4	$59.39	6.248%	$63.1007	$63.10	$63.10	$63.10
Purchase #5	$228.87	6.173%	$242.9981	$243.00	$243.00	$243.00
Purchase #6	$200.80	9.235%	$219.3439	$219.34	$219.35	$219.30
Purchase #7	$74.97	10.167%	$82.5922	$82.59	$82.60	$82.60
7 purchase totals =	$943.06		$1,016.1252	$1,016.12	$1,016.15	$1,016.10