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 $114.37   10.158%   $125.9877   $125.99   $126.00   $126.00  
  Purchase #2 $208.86   13.351%   $236.7449   $236.74   $236.75   $236.70  
  Purchase #3 $16.61   13.640%   $18.8756   $18.88   $18.90   $18.90  
  Purchase #4 $241.58   10.796%   $267.661   $267.66   $267.65   $267.70  
  Purchase #5 $225.43   11.120%   $250.4978   $250.50   $250.50   $250.50  
  Purchase #6 $175.51   13.873%   $199.8585   $199.86   $199.85   $199.90  
  Purchase #7 $236.95   13.629%   $269.2439   $269.24   $269.25   $269.20  
  7 purchase totals = $1,219.31       $1,368.8694   $1,368.87   $1,368.90   $1,368.90