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	$214.61	5.680%	$226.7998	$226.80	$226.80	$226.80
Purchase #2	$13.89	3.687%	$14.4021	$14.40	$14.40	$14.40
Purchase #3	$235.45	8.709%	$255.9553	$255.96	$255.95	$256.00
Purchase #4	$203.67	3.786%	$211.3809	$211.38	$211.40	$211.40
Purchase #5	$79.38	13.311%	$89.9463	$89.95	$89.95	$89.90
Purchase #6	$37.81	12.688%	$42.6073	$42.61	$42.60	$42.60
Purchase #7	$194.57	12.425%	$218.7453	$218.75	$218.75	$218.70
7 purchase totals =	$979.38		$1,059.8370	$1,059.85	$1,059.85	$1,059.80