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 $174.92   11.815%   $195.5868   $195.59   $195.60   $195.60  
  Purchase #2 $57.34   3.238%   $59.1967   $59.20   $59.20   $59.20  
  Purchase #3 $32.61   9.349%   $35.6587   $35.66   $35.65   $35.70  
  Purchase #4 $62.41   12.801%   $70.3991   $70.40   $70.40   $70.40  
  Purchase #5 $153.90   9.269%   $168.165   $168.17   $168.15   $168.20  
  Purchase #6 $30.47   11.553%   $33.9902   $33.99   $34.00   $34.00  
  Purchase #7 $150.61   8.470%   $163.3667   $163.37   $163.35   $163.40  
  7 purchase totals = $662.26       $726.3632   $726.38   $726.35   $726.50