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 $203.90   5.748%   $215.6202   $215.62   $215.60   $215.60  
  Purchase #2 $237.74   3.681%   $246.4912   $246.49   $246.50   $246.50  
  Purchase #3 $72.28   5.511%   $76.2634   $76.26   $76.25   $76.30  
  Purchase #4 $223.45   5.867%   $236.5598   $236.56   $236.55   $236.60  
  Purchase #5 $248.76   3.779%   $258.1606   $258.16   $258.15   $258.20  
  Purchase #6 $199.28   5.635%   $210.5094   $210.51   $210.50   $210.50  
  Purchase #7 $130.46   6.523%   $138.9699   $138.97   $138.95   $139.00  
  7 purchase totals = $1,315.87       $1,382.5745   $1,382.57   $1,382.50   $1,382.70