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 $114.70   9.434%   $125.5208   $125.52   $125.50   $125.50  
  Purchase #2 $130.92   3.342%   $135.2953   $135.30   $135.30   $135.30  
  Purchase #3 $106.28   9.486%   $116.3617   $116.36   $116.35   $116.40  
  Purchase #4 $175.99   12.706%   $198.3513   $198.35   $198.35   $198.40  
  Purchase #5 $237.72   5.356%   $250.4523   $250.45   $250.45   $250.50  
  Purchase #6 $65.84   11.655%   $73.5137   $73.51   $73.50   $73.50  
  Purchase #7 $237.91   10.465%   $262.8073   $262.81   $262.80   $262.80  
  7 purchase totals = $1,069.36       $1,162.3024   $1,162.30   $1,162.25   $1,162.40