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 $195.62   5.137%   $205.669   $205.67   $205.65   $205.70  
  Purchase #2 $248.98   5.712%   $263.2017   $263.20   $263.20   $263.20  
  Purchase #3 $27.46   11.461%   $30.6072   $30.61   $30.60   $30.60  
  Purchase #4 $200.29   7.659%   $215.6302   $215.63   $215.65   $215.60  
  Purchase #5 $217.56   13.399%   $246.7109   $246.71   $246.70   $246.70  
  Purchase #6 $233.96   3.692%   $242.5978   $242.60   $242.60   $242.60  
  Purchase #7 $40.63   3.515%   $42.0581   $42.06   $42.05   $42.10  
  7 purchase totals = $1,164.50       $1,246.4749   $1,246.48   $1,246.45   $1,246.50