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 $87.55   8.566%   $95.0495   $95.05   $95.05   $95.00  
  Purchase #2 $249.89   4.560%   $261.285   $261.29   $261.30   $261.30  
  Purchase #3 $225.80   11.425%   $251.5977   $251.60   $251.60   $251.60  
  Purchase #4 $84.68   5.282%   $89.1528   $89.15   $89.15   $89.20  
  Purchase #5 $131.31   6.182%   $139.4276   $139.43   $139.45   $139.40  
  Purchase #6 $97.72   5.348%   $102.9461   $102.95   $102.95   $102.90  
  Purchase #7 $176.94   12.166%   $198.4665   $198.47   $198.45   $198.50  
  7 purchase totals = $1,053.89       $1,137.9252   $1,137.94   $1,137.95   $1,137.90