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 $62.82   11.335%   $69.9406   $69.94   $69.95   $69.90  
  Purchase #2 $62.96   13.703%   $71.5874   $71.59   $71.60   $71.60  
  Purchase #3 $205.91   5.692%   $217.6304   $217.63   $217.65   $217.60  
  Purchase #4 $93.71   5.823%   $99.1667   $99.17   $99.15   $99.20  
  Purchase #5 $119.59   4.275%   $124.7025   $124.70   $124.70   $124.70  
  Purchase #6 $55.34   9.132%   $60.3936   $60.39   $60.40   $60.40  
  Purchase #7 $10.41   13.253%   $11.7896   $11.79   $11.80   $11.80  
  7 purchase totals = $610.74       $655.2108   $655.21   $655.25   $655.20