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	$65.31	9.283%	$71.3727	$71.37	$71.35	$71.40
Purchase #2	$107.80	7.153%	$115.5109	$115.51	$115.50	$115.50
Purchase #3	$237.39	9.492%	$259.9231	$259.92	$259.90	$259.90
Purchase #4	$50.57	6.643%	$53.9294	$53.93	$53.95	$53.90
Purchase #5	$118.94	3.462%	$123.0577	$123.06	$123.05	$123.10
Purchase #6	$45.50	10.302%	$50.1874	$50.19	$50.20	$50.20
Purchase #7	$139.69	9.274%	$152.6449	$152.64	$152.65	$152.60
7 purchase totals =	$765.20		$826.6261	$826.62	$826.60	$826.60