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 $82.94   4.661%   $86.8058   $86.81   $86.80   $86.80  
  Purchase #2 $201.73   5.360%   $212.5427   $212.54   $212.55   $212.50  
  Purchase #3 $65.55   13.225%   $74.219   $74.22   $74.20   $74.20  
  Purchase #4 $204.43   9.699%   $224.2577   $224.26   $224.25   $224.30  
  Purchase #5 $237.25   12.654%   $267.2716   $267.27   $267.25   $267.30  
  Purchase #6 $250.58   9.250%   $273.7587   $273.76   $273.75   $273.80  
  Purchase #7 $25.41   7.675%   $27.3602   $27.36   $27.35   $27.40  
  7 purchase totals = $1,067.89       $1,166.2157   $1,166.22   $1,166.15   $1,166.30