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 $198.35   5.755%   $209.765   $209.77   $209.75   $209.80  
  Purchase #2 $196.37   10.452%   $216.8946   $216.89   $216.90   $216.90  
  Purchase #3 $24.97   6.619%   $26.6228   $26.62   $26.60   $26.60  
  Purchase #4 $26.25   12.757%   $29.5987   $29.60   $29.60   $29.60  
  Purchase #5 $152.91   6.844%   $163.3752   $163.38   $163.40   $163.40  
  Purchase #6 $113.25   5.797%   $119.8151   $119.82   $119.80   $119.80  
  Purchase #7 $209.53   12.395%   $235.5012   $235.50   $235.50   $235.50  
  7 purchase totals = $921.63       $1,001.5726   $1,001.58   $1,001.55   $1,001.60