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	$205.41	12.758%	$231.6162	$231.62	$231.60	$231.60
Purchase #2	$193.43	12.127%	$216.8873	$216.89	$216.90	$216.90
Purchase #3	$48.85	5.573%	$51.5724	$51.57	$51.55	$51.60
Purchase #4	$179.70	11.534%	$200.4266	$200.43	$200.45	$200.40
Purchase #5	$159.89	8.487%	$173.4599	$173.46	$173.45	$173.50
Purchase #6	$5.35	3.686%	$5.5472	$5.55	$5.55	$5.50
Purchase #7	$119.55	3.264%	$123.4521	$123.45	$123.45	$123.50
7 purchase totals =	$912.18		$1,002.9617	$1,002.97	$1,002.95	$1,003.00