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 $233.51   10.605%   $258.2737   $258.27   $258.25   $258.30  
  Purchase #2 $168.43   3.108%   $173.6648   $173.66   $173.65   $173.70  
  Purchase #3 $69.95   9.574%   $76.647   $76.65   $76.65   $76.60  
  Purchase #4 $150.47   7.443%   $161.6695   $161.67   $161.65   $161.70  
  Purchase #5 $22.45   12.491%   $25.2542   $25.25   $25.25   $25.30  
  Purchase #6 $198.26   5.620%   $209.4022   $209.40   $209.40   $209.40  
  Purchase #7 $189.64   4.225%   $197.6523   $197.65   $197.65   $197.70  
  7 purchase totals = $1,032.71       $1,102.5637   $1,102.55   $1,102.50   $1,102.70