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 $41.65   9.359%   $45.548   $45.55   $45.55   $45.50  
  Purchase #2 $149.70   13.311%   $169.6266   $169.63   $169.65   $169.60  
  Purchase #3 $158.95   5.412%   $167.5524   $167.55   $167.55   $167.60  
  Purchase #4 $231.88   12.530%   $260.9346   $260.93   $260.95   $260.90  
  Purchase #5 $122.89   3.229%   $126.8581   $126.86   $126.85   $126.90  
  Purchase #6 $154.84   13.349%   $175.5096   $175.51   $175.50   $175.50  
  Purchase #7 $106.55   6.698%   $113.6867   $113.69   $113.70   $113.70  
  7 purchase totals = $966.46       $1,059.7160   $1,059.72   $1,059.75   $1,059.70