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	$96.59	12.788%	$108.9419	$108.94	$108.95	$108.90
Purchase #2	$52.55	9.710%	$57.6526	$57.65	$57.65	$57.70
Purchase #3	$143.57	5.202%	$151.0385	$151.04	$151.05	$151.00
Purchase #4	$224.36	7.612%	$241.4383	$241.44	$241.45	$241.40
Purchase #5	$63.89	12.655%	$71.9753	$71.98	$72.00	$72.00
Purchase #6	$134.54	6.749%	$143.6201	$143.62	$143.60	$143.60
Purchase #7	$49.75	10.275%	$54.8618	$54.86	$54.85	$54.90
7 purchase totals =	$765.25		$829.5285	$829.53	$829.55	$829.50