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 $215.66   6.524%   $229.7297   $229.73   $229.75   $229.70  
  Purchase #2 $118.61   4.261%   $123.664   $123.66   $123.65   $123.70  
  Purchase #3 $214.52   11.731%   $239.6853   $239.69   $239.70   $239.70  
  Purchase #4 $204.95   6.682%   $218.6448   $218.64   $218.65   $218.60  
  Purchase #5 $211.62   11.407%   $235.7595   $235.76   $235.75   $235.80  
  Purchase #6 $230.72   10.830%   $255.707   $255.71   $255.70   $255.70  
  Purchase #7 $236.99   5.725%   $250.5577   $250.56   $250.55   $250.60  
  7 purchase totals = $1,433.07       $1,553.7480   $1,553.75   $1,553.75   $1,553.80