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	$222.62	6.294%	$236.6317	$236.63	$236.65	$236.60
Purchase #2	$164.95	4.583%	$172.5097	$172.51	$172.50	$172.50
Purchase #3	$32.28	3.665%	$33.4631	$33.46	$33.45	$33.50
Purchase #4	$166.43	9.830%	$182.7901	$182.79	$182.80	$182.80
Purchase #5	$14.83	9.865%	$16.293	$16.29	$16.30	$16.30
Purchase #6	$38.77	13.539%	$44.0191	$44.02	$44.00	$44.00
Purchase #7	$85.53	5.395%	$90.1443	$90.14	$90.15	$90.10
7 purchase totals =	$725.41		$775.8510	$775.84	$775.85	$775.80