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 $220.27   11.342%   $245.253   $245.25   $245.25   $245.30  
  Purchase #2 $105.37   13.266%   $119.3484   $119.35   $119.35   $119.30  
  Purchase #3 $17.73   4.863%   $18.5922   $18.59   $18.60   $18.60  
  Purchase #4 $58.48   6.465%   $62.2607   $62.26   $62.25   $62.30  
  Purchase #5 $114.57   3.424%   $118.4929   $118.49   $118.50   $118.50  
  Purchase #6 $190.47   13.531%   $216.2425   $216.24   $216.25   $216.20  
  Purchase #7 $242.32   11.239%   $269.5543   $269.55   $269.55   $269.60  
  7 purchase totals = $949.21       $1,049.7440   $1,049.73   $1,049.75   $1,049.80