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 $42.72   9.118%   $46.6152   $46.62   $46.60   $46.60  
  Purchase #2 $157.66   10.835%   $174.7425   $174.74   $174.75   $174.70  
  Purchase #3 $106.88   11.873%   $119.5699   $119.57   $119.55   $119.60  
  Purchase #4 $96.44   6.433%   $102.644   $102.64   $102.65   $102.60  
  Purchase #5 $53.42   6.874%   $57.0921   $57.09   $57.10   $57.10  
  Purchase #6 $247.73   5.837%   $262.19   $262.19   $262.20   $262.20  
  Purchase #7 $161.72   7.730%   $174.221   $174.22   $174.20   $174.20  
  7 purchase totals = $866.57       $937.0747   $937.07   $937.05   $937.00