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	$38.93	4.835%	$40.8123	$40.81	$40.80	$40.80
Purchase #2	$231.79	8.558%	$251.6266	$251.63	$251.65	$251.60
Purchase #3	$150.78	10.320%	$166.3405	$166.34	$166.35	$166.30
Purchase #4	$225.57	7.596%	$242.7043	$242.70	$242.70	$242.70
Purchase #5	$154.39	9.172%	$168.5507	$168.55	$168.55	$168.60
Purchase #6	$176.85	11.138%	$196.5476	$196.55	$196.55	$196.50
Purchase #7	$166.47	4.836%	$174.5205	$174.52	$174.50	$174.50
7 purchase totals =	$1,144.78		$1,241.1025	$1,241.10	$1,241.10	$1,241.00