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 $87.74   8.216%   $94.9487   $94.95   $94.95   $94.90  
  Purchase #2 $239.72   5.799%   $253.6214   $253.62   $253.60   $253.60  
  Purchase #3 $143.60   12.337%   $161.3159   $161.32   $161.30   $161.30  
  Purchase #4 $69.28   9.500%   $75.8616   $75.86   $75.85   $75.90  
  Purchase #5 $103.71   9.556%   $113.6205   $113.62   $113.60   $113.60  
  Purchase #6 $218.68   4.673%   $228.8989   $228.90   $228.90   $228.90  
  Purchase #7 $200.73   8.322%   $217.4348   $217.43   $217.45   $217.40  
  7 purchase totals = $1,063.46       $1,145.7018   $1,145.70   $1,145.65   $1,145.60