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 $84.57   12.301%   $94.973   $94.97   $94.95   $95.00  
  Purchase #2 $146.71   12.393%   $164.8918   $164.89   $164.90   $164.90  
  Purchase #3 $52.32   12.229%   $58.7182   $58.72   $58.70   $58.70  
  Purchase #4 $139.30   6.664%   $148.583   $148.58   $148.60   $148.60  
  Purchase #5 $224.93   10.808%   $249.2404   $249.24   $249.25   $249.20  
  Purchase #6 $98.79   10.752%   $109.4119   $109.41   $109.40   $109.40  
  Purchase #7 $189.80   10.113%   $208.9945   $208.99   $209.00   $209.00  
  7 purchase totals = $936.42       $1,034.8128   $1,034.80   $1,034.80   $1,034.80