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 $24.36   6.772%   $26.0097   $26.01   $26.00   $26.00  
  Purchase #2 $234.81   5.676%   $248.1378   $248.14   $248.15   $248.10  
  Purchase #3 $157.49   8.857%   $171.4389   $171.44   $171.45   $171.40  
  Purchase #4 $126.29   4.629%   $132.136   $132.14   $132.15   $132.10  
  Purchase #5 $71.83   7.270%   $77.052   $77.05   $77.05   $77.10  
  Purchase #6 $152.80   9.328%   $167.0532   $167.05   $167.05   $167.10  
  Purchase #7 $243.95   9.439%   $266.9764   $266.98   $267.00   $267.00  
  7 purchase totals = $1,011.53       $1,088.8040   $1,088.81   $1,088.85   $1,088.80