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 $58.42   8.721%   $63.5148   $63.51   $63.50   $63.50  
  Purchase #2 $214.35   10.474%   $236.801   $236.80   $236.80   $236.80  
  Purchase #3 $159.51   7.151%   $170.9166   $170.92   $170.90   $170.90  
  Purchase #4 $155.37   13.428%   $176.2331   $176.23   $176.25   $176.20  
  Purchase #5 $98.40   9.828%   $108.0708   $108.07   $108.05   $108.10  
  Purchase #6 $125.81   10.812%   $139.4126   $139.41   $139.40   $139.40  
  Purchase #7 $170.83   11.848%   $191.0699   $191.07   $191.05   $191.10  
  7 purchase totals = $982.69       $1,086.0188   $1,086.01   $1,085.95   $1,086.00