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	$161.86	6.786%	$172.8438	$172.84	$172.85	$172.80
Purchase #2	$138.81	3.345%	$143.4532	$143.45	$143.45	$143.50
Purchase #3	$52.36	13.551%	$59.4553	$59.46	$59.45	$59.50
Purchase #4	$166.76	13.837%	$189.8346	$189.83	$189.85	$189.80
Purchase #5	$124.44	10.676%	$137.7252	$137.73	$137.75	$137.70
Purchase #6	$145.63	4.859%	$152.7062	$152.71	$152.70	$152.70
Purchase #7	$187.36	7.242%	$200.9286	$200.93	$200.95	$200.90
7 purchase totals =	$977.22		$1,056.9469	$1,056.95	$1,057.00	$1,056.90