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 $87.86   5.527%   $92.716   $92.72   $92.70   $92.70  
  Purchase #2 $191.78   4.848%   $201.0775   $201.08   $201.10   $201.10  
  Purchase #3 $41.89   3.660%   $43.4232   $43.42   $43.40   $43.40  
  Purchase #4 $102.55   5.473%   $108.1626   $108.16   $108.15   $108.20  
  Purchase #5 $69.72   10.221%   $76.8461   $76.85   $76.85   $76.80  
  Purchase #6 $231.46   6.595%   $246.7248   $246.72   $246.70   $246.70  
  Purchase #7 $155.49   6.358%   $165.3761   $165.38   $165.40   $165.40  
  7 purchase totals = $880.75       $934.3263   $934.33   $934.30   $934.30