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	$152.29	9.581%	$166.8809	$166.88	$166.90	$166.90
Purchase #2	$236.99	8.247%	$256.5346	$256.53	$256.55	$256.50
Purchase #3	$37.34	7.715%	$40.2208	$40.22	$40.20	$40.20
Purchase #4	$19.46	4.693%	$20.3733	$20.37	$20.35	$20.40
Purchase #5	$10.90	9.521%	$11.9378	$11.94	$11.95	$11.90
Purchase #6	$62.67	4.604%	$65.5553	$65.56	$65.55	$65.60
Purchase #7	$190.82	12.538%	$214.745	$214.75	$214.75	$214.70
7 purchase totals =	$710.47		$776.2477	$776.25	$776.25	$776.20