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	$43.70	11.203%	$48.5957	$48.60	$48.60	$48.60
Purchase #2	$189.84	11.806%	$212.2525	$212.25	$212.25	$212.30
Purchase #3	$30.53	4.590%	$31.9313	$31.93	$31.95	$31.90
Purchase #4	$40.86	10.440%	$45.1258	$45.13	$45.15	$45.10
Purchase #5	$123.55	11.190%	$137.3752	$137.38	$137.40	$137.40
Purchase #6	$207.82	8.449%	$225.3787	$225.38	$225.40	$225.40
Purchase #7	$227.41	6.747%	$242.7534	$242.75	$242.75	$242.80
7 purchase totals =	$863.71		$943.4126	$943.42	$943.50	$943.50