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	$132.84	5.534%	$140.1914	$140.19	$140.20	$140.20
Purchase #2	$119.77	3.334%	$123.7631	$123.76	$123.75	$123.80
Purchase #3	$203.65	12.668%	$229.4484	$229.45	$229.45	$229.40
Purchase #4	$139.75	8.364%	$151.4387	$151.44	$151.45	$151.40
Purchase #5	$131.56	6.513%	$140.1285	$140.13	$140.15	$140.10
Purchase #6	$172.29	8.837%	$187.5153	$187.52	$187.50	$187.50
Purchase #7	$81.67	10.307%	$90.0877	$90.09	$90.10	$90.10
7 purchase totals =	$981.53		$1,062.5731	$1,062.58	$1,062.60	$1,062.50