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	$108.47	3.749%	$112.5365	$112.54	$112.55	$112.50
Purchase #2	$97.32	6.484%	$103.6302	$103.63	$103.65	$103.60
Purchase #3	$144.72	8.871%	$157.5581	$157.56	$157.55	$157.60
Purchase #4	$181.82	9.186%	$198.522	$198.52	$198.50	$198.50
Purchase #5	$156.78	6.455%	$166.9001	$166.90	$166.90	$166.90
Purchase #6	$79.46	6.820%	$84.8792	$84.88	$84.90	$84.90
Purchase #7	$241.79	8.568%	$262.5066	$262.51	$262.50	$262.50
7 purchase totals =	$1,010.36		$1,086.5327	$1,086.54	$1,086.55	$1,086.50