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	$105.48	6.872%	$112.7286	$112.73	$112.75	$112.70
Purchase #2	$22.79	3.233%	$23.5268	$23.53	$23.55	$23.50
Purchase #3	$51.33	11.534%	$57.2504	$57.25	$57.25	$57.30
Purchase #4	$94.98	8.587%	$103.1359	$103.14	$103.15	$103.10
Purchase #5	$93.57	12.691%	$105.445	$105.45	$105.45	$105.40
Purchase #6	$217.55	4.609%	$227.5769	$227.58	$227.60	$227.60
Purchase #7	$129.94	11.275%	$144.5907	$144.59	$144.60	$144.60
7 purchase totals =	$715.64		$774.2543	$774.27	$774.35	$774.20