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 $60.89   13.262%   $68.9652   $68.97   $68.95   $69.00  
  Purchase #2 $53.58   10.554%   $59.2348   $59.23   $59.25   $59.20  
  Purchase #3 $238.65   3.771%   $247.6495   $247.65   $247.65   $247.60  
  Purchase #4 $188.57   6.768%   $201.3324   $201.33   $201.35   $201.30  
  Purchase #5 $190.66   8.127%   $206.1549   $206.15   $206.15   $206.20  
  Purchase #6 $17.78   5.448%   $18.7487   $18.75   $18.75   $18.70  
  Purchase #7 $227.76   7.856%   $245.6528   $245.65   $245.65   $245.70  
  7 purchase totals = $977.89       $1,047.7383   $1,047.73   $1,047.75   $1,047.70