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 $84.89   11.741%   $94.8569   $94.86   $94.85   $94.90  
  Purchase #2 $177.77   7.293%   $190.7348   $190.73   $190.75   $190.70  
  Purchase #3 $208.55   13.103%   $235.8763   $235.88   $235.90   $235.90  
  Purchase #4 $237.40   10.396%   $262.0801   $262.08   $262.10   $262.10  
  Purchase #5 $238.69   11.510%   $266.1632   $266.16   $266.15   $266.20  
  Purchase #6 $68.56   9.324%   $74.9525   $74.95   $74.95   $75.00  
  Purchase #7 $28.61   9.219%   $31.2476   $31.25   $31.25   $31.20  
  7 purchase totals = $1,044.47       $1,155.9114   $1,155.91   $1,155.95   $1,156.00