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 $23.75   10.212%   $26.1754   $26.18   $26.20   $26.20  
  Purchase #2 $134.79   5.287%   $141.9163   $141.92   $141.90   $141.90  
  Purchase #3 $188.47   6.721%   $201.1371   $201.14   $201.15   $201.10  
  Purchase #4 $63.71   6.386%   $67.7785   $67.78   $67.80   $67.80  
  Purchase #5 $48.87   5.136%   $51.38   $51.38   $51.40   $51.40  
  Purchase #6 $54.51   6.625%   $58.1213   $58.12   $58.10   $58.10  
  Purchase #7 $175.52   5.750%   $185.6124   $185.61   $185.60   $185.60  
  7 purchase totals = $689.62       $732.1210   $732.13   $732.15   $732.10