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	$20.96	13.643%	$23.8196	$23.82	$23.80	$23.80
Purchase #2	$69.29	13.488%	$78.6358	$78.64	$78.65	$78.60
Purchase #3	$116.37	6.253%	$123.6466	$123.65	$123.65	$123.60
Purchase #4	$100.49	12.482%	$113.0332	$113.03	$113.05	$113.00
Purchase #5	$86.45	7.337%	$92.7928	$92.79	$92.80	$92.80
Purchase #6	$82.81	4.586%	$86.6077	$86.61	$86.60	$86.60
Purchase #7	$227.62	6.708%	$242.8887	$242.89	$242.90	$242.90
7 purchase totals =	$703.99		$761.4244	$761.43	$761.45	$761.30