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 $216.41   9.149%   $236.2094   $236.21   $236.20   $236.20  
  Purchase #2 $61.68   8.293%   $66.7951   $66.80   $66.80   $66.80  
  Purchase #3 $16.78   9.454%   $18.3664   $18.37   $18.35   $18.40  
  Purchase #4 $102.32   6.719%   $109.1949   $109.19   $109.20   $109.20  
  Purchase #5 $218.56   6.257%   $232.2353   $232.24   $232.25   $232.20  
  Purchase #6 $102.81   8.711%   $111.7658   $111.77   $111.75   $111.80  
  Purchase #7 $179.65   11.823%   $200.89   $200.89   $200.90   $200.90  
  7 purchase totals = $898.21       $975.4569   $975.47   $975.45   $975.50