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 $55.41   13.574%   $62.9314   $62.93   $62.95   $62.90  
  Purchase #2 $179.71   10.272%   $198.1698   $198.17   $198.15   $198.20  
  Purchase #3 $86.87   9.110%   $94.7839   $94.78   $94.80   $94.80  
  Purchase #4 $54.84   13.353%   $62.1628   $62.16   $62.15   $62.20  
  Purchase #5 $9.37   8.273%   $10.1452   $10.15   $10.15   $10.10  
  Purchase #6 $212.45   3.642%   $220.1874   $220.19   $220.20   $220.20  
  Purchase #7 $189.56   11.649%   $211.6418   $211.64   $211.65   $211.60  
  7 purchase totals = $788.21       $860.0223   $860.02   $860.05   $860.00