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 $104.82   8.782%   $114.0253   $114.03   $114.05   $114.00  
  Purchase #2 $155.76   11.143%   $173.1163   $173.12   $173.10   $173.10  
  Purchase #3 $85.71   11.108%   $95.2307   $95.23   $95.25   $95.20  
  Purchase #4 $61.58   8.329%   $66.709   $66.71   $66.70   $66.70  
  Purchase #5 $248.71   13.570%   $282.4599   $282.46   $282.45   $282.50  
  Purchase #6 $97.43   9.126%   $106.3215   $106.32   $106.30   $106.30  
  Purchase #7 $164.87   3.648%   $170.8845   $170.88   $170.90   $170.90  
  7 purchase totals = $918.88       $1,008.7472   $1,008.75   $1,008.75   $1,008.70