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	$43.78	6.441%	$46.5999	$46.60	$46.60	$46.60
Purchase #2	$229.55	3.503%	$237.5911	$237.59	$237.60	$237.60
Purchase #3	$42.39	6.664%	$45.2149	$45.21	$45.20	$45.20
Purchase #4	$99.88	11.756%	$111.6219	$111.62	$111.60	$111.60
Purchase #5	$121.99	12.408%	$137.1265	$137.13	$137.15	$137.10
Purchase #6	$190.85	4.462%	$199.3657	$199.37	$199.35	$199.40
Purchase #7	$156.68	9.431%	$171.4565	$171.46	$171.45	$171.50
7 purchase totals =	$885.12		$948.9765	$948.98	$948.95	$949.00