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	$207.86	9.250%	$227.0871	$227.09	$227.10	$227.10
Purchase #2	$135.55	10.291%	$149.4995	$149.50	$149.50	$149.50
Purchase #3	$103.95	8.822%	$113.1205	$113.12	$113.10	$113.10
Purchase #4	$65.70	10.483%	$72.5873	$72.59	$72.60	$72.60
Purchase #5	$180.98	12.616%	$203.8124	$203.81	$203.80	$203.80
Purchase #6	$82.27	9.377%	$89.9845	$89.98	$90.00	$90.00
Purchase #7	$177.82	3.726%	$184.4456	$184.45	$184.45	$184.40
7 purchase totals =	$954.13		$1,040.5369	$1,040.54	$1,040.55	$1,040.50