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 $195.69   4.570%   $204.633   $204.63   $204.65   $204.60  
  Purchase #2 $154.39   13.785%   $175.6727   $175.67   $175.65   $175.70  
  Purchase #3 $202.95   11.601%   $226.4942   $226.49   $226.50   $226.50  
  Purchase #4 $104.93   10.177%   $115.6087   $115.61   $115.60   $115.60  
  Purchase #5 $214.31   3.368%   $221.528   $221.53   $221.55   $221.50  
  Purchase #6 $222.48   4.726%   $232.9944   $232.99   $233.00   $233.00  
  Purchase #7 $21.32   13.819%   $24.2662   $24.27   $24.25   $24.30  
  7 purchase totals = $1,116.07       $1,201.1972   $1,201.19   $1,201.20   $1,201.20