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	$174.52	3.104%	$179.9371	$179.94	$179.95	$179.90
Purchase #2	$143.39	4.612%	$150.0031	$150.00	$150.00	$150.00
Purchase #3	$164.72	13.624%	$187.1615	$187.16	$187.15	$187.20
Purchase #4	$117.29	4.869%	$123.0009	$123.00	$123.00	$123.00
Purchase #5	$135.46	7.838%	$146.0774	$146.08	$146.10	$146.10
Purchase #6	$45.48	13.419%	$51.583	$51.58	$51.60	$51.60
Purchase #7	$135.97	6.192%	$144.3893	$144.39	$144.40	$144.40
7 purchase totals =	$916.83		$982.1523	$982.15	$982.20	$982.20