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	$57.76	6.622%	$61.5849	$61.58	$61.60	$61.60
Purchase #2	$43.54	11.415%	$48.5101	$48.51	$48.50	$48.50
Purchase #3	$164.39	4.531%	$171.8385	$171.84	$171.85	$171.80
Purchase #4	$145.85	9.287%	$159.3951	$159.40	$159.40	$159.40
Purchase #5	$243.71	7.658%	$262.3733	$262.37	$262.35	$262.40
Purchase #6	$172.78	8.616%	$187.6667	$187.67	$187.65	$187.70
Purchase #7	$28.70	9.762%	$31.5017	$31.50	$31.50	$31.50
7 purchase totals =	$856.73		$922.8703	$922.87	$922.85	$922.90