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 $56.73   10.745%   $62.8256   $62.83   $62.85   $62.80  
  Purchase #2 $240.78   10.509%   $266.0836   $266.08   $266.10   $266.10  
  Purchase #3 $76.40   7.677%   $82.2652   $82.27   $82.25   $82.30  
  Purchase #4 $217.40   4.364%   $226.8873   $226.89   $226.90   $226.90  
  Purchase #5 $59.91   5.482%   $63.1943   $63.19   $63.20   $63.20  
  Purchase #6 $149.27   13.237%   $169.0289   $169.03   $169.05   $169.00  
  Purchase #7 $125.27   8.351%   $135.7313   $135.73   $135.75   $135.70  
  7 purchase totals = $925.76       $1,006.0162   $1,006.02   $1,006.10   $1,006.00