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 $57.59   8.182%   $62.302   $62.30   $62.30   $62.30  
  Purchase #2 $230.46   6.728%   $245.9653   $245.97   $245.95   $246.00  
  Purchase #3 $229.64   12.516%   $258.3817   $258.38   $258.40   $258.40  
  Purchase #4 $77.42   3.159%   $79.8657   $79.87   $79.85   $79.90  
  Purchase #5 $250.25   7.758%   $269.6644   $269.66   $269.65   $269.70  
  Purchase #6 $140.48   9.658%   $154.0476   $154.05   $154.05   $154.00  
  Purchase #7 $166.81   8.203%   $180.4934   $180.49   $180.50   $180.50  
  7 purchase totals = $1,152.65       $1,250.7201   $1,250.72   $1,250.70   $1,250.80