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 $57.84   7.628%   $62.252   $62.25   $62.25   $62.30  
  Purchase #2 $154.86   5.618%   $163.56   $163.56   $163.55   $163.60  
  Purchase #3 $34.95   8.630%   $37.9662   $37.97   $37.95   $38.00  
  Purchase #4 $89.99   9.480%   $98.5211   $98.52   $98.50   $98.50  
  Purchase #5 $165.73   6.127%   $175.8843   $175.88   $175.90   $175.90  
  Purchase #6 $223.49   9.652%   $245.0613   $245.06   $245.05   $245.10  
  Purchase #7 $178.86   13.525%   $203.0508   $203.05   $203.05   $203.10  
  7 purchase totals = $905.72       $986.2957   $986.29   $986.25   $986.50