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 $60.56   3.778%   $62.848   $62.85   $62.85   $62.80  
  Purchase #2 $165.28   8.127%   $178.7123   $178.71   $178.70   $178.70  
  Purchase #3 $141.49   13.140%   $160.0818   $160.08   $160.10   $160.10  
  Purchase #4 $246.65   10.241%   $271.9094   $271.91   $271.90   $271.90  
  Purchase #5 $60.71   8.157%   $65.6621   $65.66   $65.65   $65.70  
  Purchase #6 $228.44   12.448%   $256.8762   $256.88   $256.90   $256.90  
  Purchase #7 $35.79   13.260%   $40.5358   $40.54   $40.55   $40.50  
  7 purchase totals = $938.92       $1,036.6256   $1,036.63   $1,036.65   $1,036.60