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	$64.78	4.499%	$67.6945	$67.69	$67.70	$67.70
Purchase #2	$242.64	6.757%	$259.0352	$259.04	$259.05	$259.00
Purchase #3	$143.53	10.536%	$158.6523	$158.65	$158.65	$158.70
Purchase #4	$99.77	3.850%	$103.6111	$103.61	$103.60	$103.60
Purchase #5	$49.35	3.630%	$51.1414	$51.14	$51.15	$51.10
Purchase #6	$216.39	6.799%	$231.1024	$231.10	$231.10	$231.10
Purchase #7	$49.83	13.323%	$56.4689	$56.47	$56.45	$56.50
7 purchase totals =	$866.29		$927.7058	$927.70	$927.70	$927.70