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	$242.27	3.398%	$250.5023	$250.50	$250.50	$250.50
Purchase #2	$44.67	7.465%	$48.0046	$48.00	$48.00	$48.00
Purchase #3	$74.61	5.203%	$78.492	$78.49	$78.50	$78.50
Purchase #4	$46.36	5.338%	$48.8347	$48.83	$48.85	$48.80
Purchase #5	$118.98	10.843%	$131.881	$131.88	$131.90	$131.90
Purchase #6	$156.83	8.128%	$169.5771	$169.58	$169.60	$169.60
Purchase #7	$189.76	5.585%	$200.3581	$200.36	$200.35	$200.40
7 purchase totals =	$873.48		$927.6498	$927.64	$927.70	$927.70