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 $215.47   8.307%   $233.3691   $233.37   $233.35   $233.40  
  Purchase #2 $225.89   4.601%   $236.2832   $236.28   $236.30   $236.30  
  Purchase #3 $96.68   13.553%   $109.783   $109.78   $109.80   $109.80  
  Purchase #4 $146.93   5.591%   $155.1449   $155.14   $155.15   $155.10  
  Purchase #5 $146.57   12.286%   $164.5776   $164.58   $164.60   $164.60  
  Purchase #6 $44.78   4.345%   $46.7257   $46.73   $46.75   $46.70  
  Purchase #7 $233.65   10.389%   $257.9239   $257.92   $257.90   $257.90  
  7 purchase totals = $1,109.97       $1,203.8074   $1,203.80   $1,203.85   $1,203.80