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	$242.71	9.587%	$265.9786	$265.98	$266.00	$266.00
Purchase #2	$142.58	13.292%	$161.5317	$161.53	$161.55	$161.50
Purchase #3	$155.60	7.330%	$167.0055	$167.01	$167.00	$167.00
Purchase #4	$153.95	9.461%	$168.5152	$168.52	$168.50	$168.50
Purchase #5	$19.32	11.146%	$21.4734	$21.47	$21.45	$21.50
Purchase #6	$170.52	12.355%	$191.5877	$191.59	$191.60	$191.60
Purchase #7	$68.34	5.105%	$71.8288	$71.83	$71.85	$71.80
7 purchase totals =	$953.02		$1,047.9209	$1,047.93	$1,047.95	$1,047.90