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 $61.84   12.363%   $69.4853   $69.49   $69.50   $69.50  
  Purchase #2 $62.56   6.384%   $66.5538   $66.55   $66.55   $66.60  
  Purchase #3 $81.80   12.219%   $91.7951   $91.80   $91.80   $91.80  
  Purchase #4 $33.76   4.170%   $35.1678   $35.17   $35.15   $35.20  
  Purchase #5 $37.33   8.787%   $40.6102   $40.61   $40.60   $40.60  
  Purchase #6 $217.67   5.473%   $229.5831   $229.58   $229.60   $229.60  
  Purchase #7 $158.78   5.636%   $167.7288   $167.73   $167.75   $167.70  
  7 purchase totals = $653.74       $700.9241   $700.93   $700.95   $701.00