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 $84.88   10.426%   $93.7296   $93.73   $93.75   $93.70  
  Purchase #2 $227.87   13.146%   $257.8258   $257.83   $257.85   $257.80  
  Purchase #3 $190.25   3.251%   $196.435   $196.44   $196.45   $196.40  
  Purchase #4 $71.34   5.836%   $75.5034   $75.50   $75.50   $75.50  
  Purchase #5 $233.46   6.394%   $248.3874   $248.39   $248.40   $248.40  
  Purchase #6 $58.66   12.717%   $66.1198   $66.12   $66.10   $66.10  
  Purchase #7 $68.60   10.862%   $76.0513   $76.05   $76.05   $76.10  
  7 purchase totals = $935.06       $1,014.0523   $1,014.06   $1,014.10   $1,014.00