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 $196.67   5.839%   $208.1536   $208.15   $208.15   $208.20  
  Purchase #2 $65.65   11.432%   $73.1551   $73.16   $73.15   $73.20  
  Purchase #3 $192.64   13.658%   $218.9508   $218.95   $218.95   $219.00  
  Purchase #4 $87.32   7.291%   $93.6865   $93.69   $93.70   $93.70  
  Purchase #5 $221.88   11.562%   $247.5338   $247.53   $247.55   $247.50  
  Purchase #6 $228.71   12.353%   $256.9625   $256.96   $256.95   $257.00  
  Purchase #7 $63.46   5.158%   $66.7333   $66.73   $66.75   $66.70  
  7 purchase totals = $1,056.33       $1,165.1756   $1,165.17   $1,165.20   $1,165.30