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	$111.77	6.792%	$119.3614	$119.36	$119.35	$119.40
Purchase #2	$214.77	12.804%	$242.2692	$242.27	$242.25	$242.30
Purchase #3	$26.60	9.168%	$29.0387	$29.04	$29.05	$29.00
Purchase #4	$218.82	10.587%	$241.9865	$241.99	$242.00	$242.00
Purchase #5	$250.70	3.366%	$259.1386	$259.14	$259.15	$259.10
Purchase #6	$43.67	3.190%	$45.0631	$45.06	$45.05	$45.10
Purchase #7	$169.42	12.506%	$190.6077	$190.61	$190.60	$190.60
7 purchase totals =	$1,035.75		$1,127.4652	$1,127.47	$1,127.45	$1,127.50