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 $81.53   5.706%   $86.1821   $86.18   $86.20   $86.20  
  Purchase #2 $224.42   7.582%   $241.4355   $241.44   $241.45   $241.40  
  Purchase #3 $45.43   10.118%   $50.0266   $50.03   $50.05   $50.00  
  Purchase #4 $242.26   6.154%   $257.1687   $257.17   $257.15   $257.20  
  Purchase #5 $26.33   4.593%   $27.5393   $27.54   $27.55   $27.50  
  Purchase #6 $163.95   11.746%   $183.2076   $183.21   $183.20   $183.20  
  Purchase #7 $247.33   5.398%   $260.6809   $260.68   $260.70   $260.70  
  7 purchase totals = $1,031.25       $1,106.2407   $1,106.25   $1,106.30   $1,106.20