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	$166.83	11.748%	$186.4292	$186.43	$186.45	$186.40
Purchase #2	$52.73	12.140%	$59.1314	$59.13	$59.15	$59.10
Purchase #3	$182.55	5.869%	$193.2639	$193.26	$193.25	$193.30
Purchase #4	$132.27	4.257%	$137.9007	$137.90	$137.90	$137.90
Purchase #5	$230.35	11.538%	$256.9278	$256.93	$256.95	$256.90
Purchase #6	$150.33	12.189%	$168.6537	$168.65	$168.65	$168.70
Purchase #7	$111.34	5.601%	$117.5762	$117.58	$117.60	$117.60
7 purchase totals =	$1,026.40		$1,119.8829	$1,119.88	$1,119.95	$1,119.90