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	$223.82	7.268%	$240.0872	$240.09	$240.10	$240.10
Purchase #2	$132.26	4.856%	$138.6825	$138.68	$138.70	$138.70
Purchase #3	$51.73	11.123%	$57.4839	$57.48	$57.50	$57.50
Purchase #4	$154.64	10.755%	$171.2715	$171.27	$171.25	$171.30
Purchase #5	$118.46	10.712%	$131.1494	$131.15	$131.15	$131.10
Purchase #6	$182.57	9.557%	$200.0182	$200.02	$200.00	$200.00
Purchase #7	$239.42	11.455%	$266.8456	$266.85	$266.85	$266.80
7 purchase totals =	$1,102.90		$1,205.5383	$1,205.54	$1,205.55	$1,205.50