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	$130.67	9.310%	$142.8354	$142.84	$142.85	$142.80
Purchase #2	$191.82	10.598%	$212.1491	$212.15	$212.15	$212.10
Purchase #3	$31.47	8.319%	$34.088	$34.09	$34.10	$34.10
Purchase #4	$143.80	4.648%	$150.4838	$150.48	$150.50	$150.50
Purchase #5	$189.76	13.153%	$214.7191	$214.72	$214.70	$214.70
Purchase #6	$122.40	8.420%	$132.7061	$132.71	$132.70	$132.70
Purchase #7	$194.43	12.432%	$218.6015	$218.60	$218.60	$218.60
7 purchase totals =	$1,004.35		$1,105.5830	$1,105.59	$1,105.60	$1,105.50