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 $32.63   6.402%   $34.719   $34.72   $34.70   $34.70  
  Purchase #2 $102.96   7.399%   $110.578   $110.58   $110.60   $110.60  
  Purchase #3 $194.59   7.531%   $209.2446   $209.24   $209.25   $209.20  
  Purchase #4 $88.36   10.855%   $97.9515   $97.95   $97.95   $98.00  
  Purchase #5 $237.71   3.188%   $245.2882   $245.29   $245.30   $245.30  
  Purchase #6 $155.90   12.799%   $175.8536   $175.85   $175.85   $175.90  
  Purchase #7 $79.56   3.448%   $82.3032   $82.30   $82.30   $82.30  
  7 purchase totals = $891.71       $955.9381   $955.93   $955.95   $956.00