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 $32.89   3.546%   $34.0563   $34.06   $34.05   $34.10  
  Purchase #2 $244.49   11.380%   $272.313   $272.31   $272.30   $272.30  
  Purchase #3 $27.46   3.400%   $28.3936   $28.39   $28.40   $28.40  
  Purchase #4 $176.26   8.391%   $191.05   $191.05   $191.05   $191.10  
  Purchase #5 $146.76   13.673%   $166.8265   $166.83   $166.85   $166.80  
  Purchase #6 $55.60   5.590%   $58.708   $58.71   $58.70   $58.70  
  Purchase #7 $199.79   5.820%   $211.4178   $211.42   $211.40   $211.40  
  7 purchase totals = $883.25       $962.7652   $962.77   $962.75   $962.80