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 $23.54   10.503%   $26.0124   $26.01   $26.00   $26.00  
  Purchase #2 $245.64   5.414%   $258.9389   $258.94   $258.95   $258.90  
  Purchase #3 $22.66   6.403%   $24.1109   $24.11   $24.10   $24.10  
  Purchase #4 $148.40   8.350%   $160.7914   $160.79   $160.80   $160.80  
  Purchase #5 $92.25   5.327%   $97.1642   $97.16   $97.15   $97.20  
  Purchase #6 $37.88   10.735%   $41.9464   $41.95   $41.95   $41.90  
  Purchase #7 $220.88   11.242%   $245.7113   $245.71   $245.70   $245.70  
  7 purchase totals = $791.25       $854.6755   $854.67   $854.65   $854.60