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 $216.56   13.363%   $245.4989   $245.50   $245.50   $245.50  
  Purchase #2 $80.95   5.249%   $85.1991   $85.20   $85.20   $85.20  
  Purchase #3 $195.97   8.568%   $212.7607   $212.76   $212.75   $212.80  
  Purchase #4 $106.39   5.430%   $112.167   $112.17   $112.15   $112.20  
  Purchase #5 $55.46   13.221%   $62.7924   $62.79   $62.80   $62.80  
  Purchase #6 $53.86   13.453%   $61.1058   $61.11   $61.10   $61.10  
  Purchase #7 $166.40   11.874%   $186.1583   $186.16   $186.15   $186.20  
  7 purchase totals = $875.59       $965.6822   $965.69   $965.65   $965.80