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 $177.61   10.136%   $195.6125   $195.61   $195.60   $195.60  
  Purchase #2 $89.84   13.404%   $101.8822   $101.88   $101.90   $101.90  
  Purchase #3 $164.91   6.186%   $175.1113   $175.11   $175.10   $175.10  
  Purchase #4 $156.56   12.190%   $175.6447   $175.64   $175.65   $175.60  
  Purchase #5 $179.91   8.665%   $195.4992   $195.50   $195.50   $195.50  
  Purchase #6 $104.71   8.791%   $113.9151   $113.92   $113.90   $113.90  
  Purchase #7 $45.27   12.846%   $51.0854   $51.09   $51.10   $51.10  
  7 purchase totals = $918.81       $1,008.7504   $1,008.75   $1,008.75   $1,008.70