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	$191.31	11.217%	$212.7692	$212.77	$212.75	$212.80
Purchase #2	$245.79	3.268%	$253.8224	$253.82	$253.80	$253.80
Purchase #3	$105.86	6.646%	$112.8955	$112.90	$112.90	$112.90
Purchase #4	$97.45	12.373%	$109.5075	$109.51	$109.50	$109.50
Purchase #5	$70.43	11.492%	$78.5238	$78.52	$78.50	$78.50
Purchase #6	$56.62	11.459%	$63.1081	$63.11	$63.10	$63.10
Purchase #7	$35.51	11.545%	$39.6096	$39.61	$39.60	$39.60
7 purchase totals =	$802.97		$870.2361	$870.24	$870.15	$870.20