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 $62.48   7.494%   $67.1623   $67.16   $67.15   $67.20  
  Purchase #2 $207.99   7.857%   $224.3318   $224.33   $224.35   $224.30  
  Purchase #3 $231.79   11.195%   $257.7389   $257.74   $257.75   $257.70  
  Purchase #4 $89.85   12.373%   $100.9671   $100.97   $100.95   $101.00  
  Purchase #5 $225.66   13.267%   $255.5983   $255.60   $255.60   $255.60  
  Purchase #6 $196.77   8.519%   $213.5328   $213.53   $213.55   $213.50  
  Purchase #7 $134.87   6.175%   $143.1982   $143.20   $143.20   $143.20  
  7 purchase totals = $1,149.41       $1,262.5294   $1,262.53   $1,262.55   $1,262.50