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	$218.90	9.571%	$239.8509	$239.85	$239.85	$239.90
Purchase #2	$18.60	12.233%	$20.8753	$20.88	$20.90	$20.90
Purchase #3	$120.74	8.624%	$131.1526	$131.15	$131.15	$131.20
Purchase #4	$179.60	11.471%	$200.2019	$200.20	$200.20	$200.20
Purchase #5	$211.50	4.483%	$220.9815	$220.98	$221.00	$221.00
Purchase #6	$132.80	6.823%	$141.8609	$141.86	$141.85	$141.90
Purchase #7	$160.66	3.859%	$166.8599	$166.86	$166.85	$166.90
7 purchase totals =	$1,042.80		$1,121.7830	$1,121.78	$1,121.80	$1,122.00