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	$102.34	13.832%	$116.4957	$116.50	$116.50	$116.50
Purchase #2	$121.97	8.632%	$132.4985	$132.50	$132.50	$132.50
Purchase #3	$126.87	8.104%	$137.1515	$137.15	$137.15	$137.20
Purchase #4	$160.89	9.722%	$176.5317	$176.53	$176.55	$176.50
Purchase #5	$156.77	5.489%	$165.3751	$165.38	$165.40	$165.40
Purchase #6	$103.40	10.819%	$114.5868	$114.59	$114.60	$114.60
Purchase #7	$96.28	6.817%	$102.8434	$102.84	$102.85	$102.80
7 purchase totals =	$868.52		$945.4827	$945.49	$945.55	$945.50