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	$216.77	10.871%	$240.3351	$240.34	$240.35	$240.30
Purchase #2	$21.76	3.801%	$22.5871	$22.59	$22.60	$22.60
Purchase #3	$176.82	9.208%	$193.1016	$193.10	$193.10	$193.10
Purchase #4	$104.67	9.208%	$114.308	$114.31	$114.30	$114.30
Purchase #5	$101.42	3.179%	$104.6441	$104.64	$104.65	$104.60
Purchase #6	$238.37	5.453%	$251.3683	$251.37	$251.35	$251.40
Purchase #7	$105.51	11.400%	$117.5381	$117.54	$117.55	$117.50
7 purchase totals =	$965.32		$1,043.8823	$1,043.89	$1,043.90	$1,043.80