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	$144.32	11.799%	$161.3483	$161.35	$161.35	$161.30
Purchase #2	$137.29	12.420%	$154.3414	$154.34	$154.35	$154.30
Purchase #3	$177.78	12.460%	$199.9314	$199.93	$199.95	$199.90
Purchase #4	$67.35	7.457%	$72.3723	$72.37	$72.35	$72.40
Purchase #5	$34.82	10.482%	$38.4698	$38.47	$38.45	$38.50
Purchase #6	$159.25	5.167%	$167.4784	$167.48	$167.50	$167.50
Purchase #7	$144.32	11.271%	$160.5863	$160.59	$160.60	$160.60
7 purchase totals =	$865.13		$954.5279	$954.53	$954.55	$954.50