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 $23.69   10.285%   $26.1265   $26.13   $26.15   $26.10  
  Purchase #2 $25.25   4.448%   $26.3731   $26.37   $26.35   $26.40  
  Purchase #3 $51.32   3.206%   $52.9653   $52.97   $52.95   $53.00  
  Purchase #4 $144.59   8.663%   $157.1158   $157.12   $157.10   $157.10  
  Purchase #5 $220.33   11.227%   $245.0664   $245.07   $245.05   $245.10  
  Purchase #6 $53.34   3.780%   $55.3563   $55.36   $55.35   $55.40  
  Purchase #7 $183.32   9.115%   $200.0296   $200.03   $200.05   $200.00  
  7 purchase totals = $701.84       $763.0330   $763.05   $763.00   $763.10