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 $241.25   10.268%   $266.0216   $266.02   $266.00   $266.00  
  Purchase #2 $224.57   10.146%   $247.3549   $247.35   $247.35   $247.40  
  Purchase #3 $213.38   4.836%   $223.6991   $223.70   $223.70   $223.70  
  Purchase #4 $228.40   8.207%   $247.1448   $247.14   $247.15   $247.10  
  Purchase #5 $41.72   10.335%   $46.0318   $46.03   $46.05   $46.00  
  Purchase #6 $205.68   9.870%   $225.9806   $225.98   $226.00   $226.00  
  Purchase #7 $217.59   3.335%   $224.8466   $224.85   $224.85   $224.80  
  7 purchase totals = $1,372.59       $1,481.0794   $1,481.07   $1,481.10   $1,481.00