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 $84.44   11.265%   $93.9522   $93.95   $93.95   $94.00  
  Purchase #2 $109.44   11.866%   $122.4262   $122.43   $122.45   $122.40  
  Purchase #3 $39.58   7.836%   $42.6815   $42.68   $42.70   $42.70  
  Purchase #4 $210.96   6.338%   $224.3306   $224.33   $224.35   $224.30  
  Purchase #5 $215.81   8.463%   $234.074   $234.07   $234.05   $234.10  
  Purchase #6 $100.42   12.533%   $113.0056   $113.01   $113.00   $113.00  
  Purchase #7 $26.38   11.360%   $29.3768   $29.38   $29.40   $29.40  
  7 purchase totals = $787.03       $859.8469   $859.85   $859.90   $859.90