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 $196.86   13.358%   $223.1566   $223.16   $223.15   $223.20  
  Purchase #2 $107.44   13.870%   $122.3419   $122.34   $122.35   $122.30  
  Purchase #3 $156.46   7.798%   $168.6608   $168.66   $168.65   $168.70  
  Purchase #4 $197.91   9.577%   $216.8638   $216.86   $216.85   $216.90  
  Purchase #5 $118.57   12.189%   $133.0225   $133.02   $133.00   $133.00  
  Purchase #6 $219.46   12.106%   $246.0278   $246.03   $246.05   $246.00  
  Purchase #7 $239.79   6.176%   $254.5994   $254.60   $254.60   $254.60  
  7 purchase totals = $1,236.49       $1,364.6728   $1,364.67   $1,364.65   $1,364.70