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 $47.27   5.245%   $49.7493   $49.75   $49.75   $49.70  
  Purchase #2 $68.54   3.811%   $71.1521   $71.15   $71.15   $71.20  
  Purchase #3 $200.87   10.169%   $221.2965   $221.30   $221.30   $221.30  
  Purchase #4 $167.57   11.161%   $186.2725   $186.27   $186.25   $186.30  
  Purchase #5 $106.34   7.229%   $114.0273   $114.03   $114.05   $114.00  
  Purchase #6 $199.27   13.199%   $225.5716   $225.57   $225.55   $225.60  
  Purchase #7 $193.40   3.856%   $200.8575   $200.86   $200.85   $200.90  
  7 purchase totals = $983.26       $1,068.9268   $1,068.93   $1,068.90   $1,069.00