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 $197.64   4.651%   $206.8322   $206.83   $206.85   $206.80  
  Purchase #2 $58.81   13.494%   $66.7458   $66.75   $66.75   $66.70  
  Purchase #3 $10.63   10.423%   $11.738   $11.74   $11.75   $11.70  
  Purchase #4 $63.46   6.637%   $67.6718   $67.67   $67.65   $67.70  
  Purchase #5 $119.26   7.596%   $128.319   $128.32   $128.30   $128.30  
  Purchase #6 $86.89   8.616%   $94.3764   $94.38   $94.40   $94.40  
  Purchase #7 $199.73   5.320%   $210.3556   $210.36   $210.35   $210.40  
  7 purchase totals = $736.42       $786.0388   $786.05   $786.05   $786.00