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	$200.61	10.861%	$222.3983	$222.40	$222.40	$222.40
Purchase #2	$224.97	12.709%	$253.5614	$253.56	$253.55	$253.60
Purchase #3	$190.59	13.217%	$215.7803	$215.78	$215.80	$215.80
Purchase #4	$25.79	6.756%	$27.5324	$27.53	$27.55	$27.50
Purchase #5	$235.25	9.641%	$257.9305	$257.93	$257.95	$257.90
Purchase #6	$103.99	6.856%	$111.1196	$111.12	$111.10	$111.10
Purchase #7	$52.27	12.204%	$58.649	$58.65	$58.65	$58.60
7 purchase totals =	$1,033.47		$1,146.9715	$1,146.97	$1,147.00	$1,146.90