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	$198.97	5.113%	$209.1433	$209.14	$209.15	$209.10
Purchase #2	$67.56	9.674%	$74.0958	$74.10	$74.10	$74.10
Purchase #3	$112.40	8.130%	$121.5381	$121.54	$121.55	$121.50
Purchase #4	$38.48	11.477%	$42.8963	$42.90	$42.90	$42.90
Purchase #5	$207.32	5.395%	$218.5049	$218.50	$218.50	$218.50
Purchase #6	$182.85	7.487%	$196.54	$196.54	$196.55	$196.50
Purchase #7	$78.40	6.347%	$83.376	$83.38	$83.40	$83.40
7 purchase totals =	$885.98		$946.0944	$946.10	$946.15	$946.00