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	$35.33	3.259%	$36.4814	$36.48	$36.50	$36.50
Purchase #2	$75.43	11.440%	$84.0592	$84.06	$84.05	$84.10
Purchase #3	$236.94	11.363%	$263.8635	$263.86	$263.85	$263.90
Purchase #4	$87.55	8.451%	$94.9489	$94.95	$94.95	$94.90
Purchase #5	$85.33	4.743%	$89.3772	$89.38	$89.40	$89.40
Purchase #6	$186.52	10.767%	$206.6026	$206.60	$206.60	$206.60
Purchase #7	$100.75	10.763%	$111.5937	$111.59	$111.60	$111.60
7 purchase totals =	$807.85		$886.9265	$886.92	$886.95	$887.00