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 $12.95   8.219%   $14.0144   $14.01   $14.00   $14.00  
  Purchase #2 $193.66   4.186%   $201.7666   $201.77   $201.75   $201.80  
  Purchase #3 $76.37   11.850%   $85.4198   $85.42   $85.40   $85.40  
  Purchase #4 $150.64   8.743%   $163.8105   $163.81   $163.80   $163.80  
  Purchase #5 $62.41   6.240%   $66.3044   $66.30   $66.30   $66.30  
  Purchase #6 $244.37   7.227%   $262.0306   $262.03   $262.05   $262.00  
  Purchase #7 $131.41   3.725%   $136.305   $136.31   $136.30   $136.30  
  7 purchase totals = $871.81       $929.6513   $929.65   $929.60   $929.60