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 $59.36   9.599%   $65.058   $65.06   $65.05   $65.10  
  Purchase #2 $162.41   4.577%   $169.8435   $169.84   $169.85   $169.80  
  Purchase #3 $235.66   4.278%   $245.7415   $245.74   $245.75   $245.70  
  Purchase #4 $238.44   9.653%   $261.4566   $261.46   $261.45   $261.50  
  Purchase #5 $124.31   9.127%   $135.6558   $135.66   $135.65   $135.70  
  Purchase #6 $19.67   3.418%   $20.3423   $20.34   $20.35   $20.30  
  Purchase #7 $136.41   7.379%   $146.4757   $146.48   $146.50   $146.50  
  7 purchase totals = $976.26       $1,044.5734   $1,044.58   $1,044.60   $1,044.60