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 $59.47   7.741%   $64.0736   $64.07   $64.05   $64.10  
  Purchase #2 $177.33   9.154%   $193.5628   $193.56   $193.55   $193.60  
  Purchase #3 $232.56   10.248%   $256.3927   $256.39   $256.40   $256.40  
  Purchase #4 $55.59   11.421%   $61.9389   $61.94   $61.95   $61.90  
  Purchase #5 $62.41   11.379%   $69.5116   $69.51   $69.50   $69.50  
  Purchase #6 $228.46   11.242%   $254.1435   $254.14   $254.15   $254.10  
  Purchase #7 $133.80   10.790%   $148.237   $148.24   $148.25   $148.20  
  7 purchase totals = $949.62       $1,047.8601   $1,047.85   $1,047.85   $1,047.80