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 $119.50   6.195%   $126.903   $126.90   $126.90   $126.90  
  Purchase #2 $69.58   5.621%   $73.4911   $73.49   $73.50   $73.50  
  Purchase #3 $174.44   5.612%   $184.2296   $184.23   $184.25   $184.20  
  Purchase #4 $14.47   13.301%   $16.3947   $16.39   $16.40   $16.40  
  Purchase #5 $226.79   5.265%   $238.7305   $238.73   $238.75   $238.70  
  Purchase #6 $186.82   11.479%   $208.2651   $208.27   $208.25   $208.30  
  Purchase #7 $174.92   12.403%   $196.6153   $196.62   $196.60   $196.60  
  7 purchase totals = $966.52       $1,044.6293   $1,044.63   $1,044.65   $1,044.60