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	$217.46	9.539%	$238.2035	$238.20	$238.20	$238.20
Purchase #2	$133.49	3.488%	$138.1461	$138.15	$138.15	$138.10
Purchase #3	$169.39	12.379%	$190.3588	$190.36	$190.35	$190.40
Purchase #4	$240.57	10.854%	$266.6815	$266.68	$266.70	$266.70
Purchase #5	$52.98	8.471%	$57.4679	$57.47	$57.45	$57.50
Purchase #6	$123.47	5.659%	$130.4572	$130.46	$130.45	$130.50
Purchase #7	$190.53	5.424%	$200.8643	$200.86	$200.85	$200.90
7 purchase totals =	$1,127.89		$1,222.1793	$1,222.18	$1,222.15	$1,222.30