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 $53.84   12.299%   $60.4618   $60.46   $60.45   $60.50  
  Purchase #2 $180.71   8.346%   $195.7921   $195.79   $195.80   $195.80  
  Purchase #3 $177.72   9.118%   $193.9245   $193.92   $193.90   $193.90  
  Purchase #4 $190.87   3.628%   $197.7948   $197.79   $197.80   $197.80  
  Purchase #5 $221.92   11.380%   $247.1745   $247.17   $247.15   $247.20  
  Purchase #6 $168.60   13.757%   $191.7943   $191.79   $191.80   $191.80  
  Purchase #7 $164.49   5.664%   $173.8067   $173.81   $173.80   $173.80  
  7 purchase totals = $1,158.15       $1,260.7487   $1,260.73   $1,260.70   $1,260.80