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 $195.45   3.230%   $201.763   $201.76   $201.75   $201.80  
  Purchase #2 $23.62   12.564%   $26.5876   $26.59   $26.60   $26.60  
  Purchase #3 $79.57   3.580%   $82.4186   $82.42   $82.40   $82.40  
  Purchase #4 $238.61   4.833%   $250.142   $250.14   $250.15   $250.10  
  Purchase #5 $88.93   8.483%   $96.4739   $96.47   $96.45   $96.50  
  Purchase #6 $112.71   12.188%   $126.4471   $126.45   $126.45   $126.40  
  Purchase #7 $195.86   8.615%   $212.7333   $212.73   $212.75   $212.70  
  7 purchase totals = $934.75       $996.5655   $996.56   $996.55   $996.50