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 $208.92   7.188%   $223.9372   $223.94   $223.95   $223.90  
  Purchase #2 $222.60   10.712%   $246.4449   $246.44   $246.45   $246.40  
  Purchase #3 $68.85   9.468%   $75.3687   $75.37   $75.35   $75.40  
  Purchase #4 $246.85   11.347%   $274.8601   $274.86   $274.85   $274.90  
  Purchase #5 $47.56   12.835%   $53.6643   $53.66   $53.65   $53.70  
  Purchase #6 $159.95   9.833%   $175.6779   $175.68   $175.70   $175.70  
  Purchase #7 $109.51   4.648%   $114.6   $114.60   $114.60   $114.60  
  7 purchase totals = $1,064.24       $1,164.5531   $1,164.55   $1,164.55   $1,164.60