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 $246.59   3.298%   $254.7225   $254.72   $254.70   $254.70  
  Purchase #2 $58.64   8.741%   $63.7657   $63.77   $63.75   $63.80  
  Purchase #3 $114.78   4.250%   $119.6582   $119.66   $119.65   $119.70  
  Purchase #4 $119.68   6.425%   $127.3694   $127.37   $127.35   $127.40  
  Purchase #5 $122.49   11.204%   $136.2138   $136.21   $136.20   $136.20  
  Purchase #6 $60.80   7.445%   $65.3266   $65.33   $65.35   $65.30  
  Purchase #7 $248.40   6.646%   $264.9087   $264.91   $264.90   $264.90  
  7 purchase totals = $971.38       $1,031.9649   $1,031.97   $1,031.90   $1,032.00