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 $87.84   8.468%   $95.2783   $95.28   $95.30   $95.30  
  Purchase #2 $215.98   13.508%   $245.1546   $245.15   $245.15   $245.20  
  Purchase #3 $15.54   11.535%   $17.3325   $17.33   $17.35   $17.30  
  Purchase #4 $140.35   3.596%   $145.397   $145.40   $145.40   $145.40  
  Purchase #5 $230.99   6.103%   $245.0873   $245.09   $245.10   $245.10  
  Purchase #6 $148.46   3.828%   $154.143   $154.14   $154.15   $154.10  
  Purchase #7 $145.63   13.792%   $165.7153   $165.72   $165.70   $165.70  
  7 purchase totals = $984.79       $1,068.1080   $1,068.11   $1,068.15   $1,068.10