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 $103.54   10.804%   $114.7265   $114.73   $114.75   $114.70  
  Purchase #2 $236.93   4.779%   $248.2529   $248.25   $248.25   $248.30  
  Purchase #3 $167.69   8.254%   $181.5311   $181.53   $181.55   $181.50  
  Purchase #4 $46.54   5.568%   $49.1313   $49.13   $49.15   $49.10  
  Purchase #5 $152.50   8.237%   $165.0614   $165.06   $165.05   $165.10  
  Purchase #6 $154.35   5.571%   $162.9488   $162.95   $162.95   $162.90  
  Purchase #7 $214.30   9.749%   $235.1921   $235.19   $235.20   $235.20  
  7 purchase totals = $1,075.85       $1,156.8441   $1,156.84   $1,156.90   $1,156.80