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 $100.72   13.623%   $114.4411   $114.44   $114.45   $114.40  
  Purchase #2 $40.85   7.596%   $43.953   $43.95   $43.95   $44.00  
  Purchase #3 $24.32   7.509%   $26.1462   $26.15   $26.15   $26.10  
  Purchase #4 $215.81   12.364%   $242.4927   $242.49   $242.50   $242.50  
  Purchase #5 $246.74   5.226%   $259.6346   $259.63   $259.65   $259.60  
  Purchase #6 $130.34   12.424%   $146.5334   $146.53   $146.55   $146.50  
  Purchase #7 $239.51   4.842%   $251.1071   $251.11   $251.10   $251.10  
  7 purchase totals = $998.29       $1,084.3081   $1,084.30   $1,084.35   $1,084.20