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	$242.39	5.750%	$256.3274	$256.33	$256.35	$256.30
Purchase #2	$136.58	5.782%	$144.4771	$144.48	$144.50	$144.50
Purchase #3	$175.45	7.741%	$189.0316	$189.03	$189.05	$189.00
Purchase #4	$32.77	8.105%	$35.426	$35.43	$35.45	$35.40
Purchase #5	$201.80	9.688%	$221.3504	$221.35	$221.35	$221.40
Purchase #6	$211.75	12.675%	$238.5893	$238.59	$238.60	$238.60
Purchase #7	$125.59	12.759%	$141.614	$141.61	$141.60	$141.60
7 purchase totals =	$1,126.33		$1,226.8158	$1,226.82	$1,226.90	$1,226.80