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 $88.38   8.447%   $95.8455   $95.85   $95.85   $95.80  
  Purchase #2 $133.77   11.319%   $148.9114   $148.91   $148.90   $148.90  
  Purchase #3 $104.83   12.265%   $117.6874   $117.69   $117.70   $117.70  
  Purchase #4 $128.41   9.816%   $141.0147   $141.01   $141.00   $141.00  
  Purchase #5 $197.64   12.592%   $222.5268   $222.53   $222.55   $222.50  
  Purchase #6 $217.30   13.356%   $246.3226   $246.32   $246.30   $246.30  
  Purchase #7 $215.34   8.632%   $233.9281   $233.93   $233.95   $233.90  
  7 purchase totals = $1,085.67       $1,206.2365   $1,206.24   $1,206.25   $1,206.10