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 $108.94   5.208%   $114.6136   $114.61   $114.60   $114.60  
  Purchase #2 $29.53   9.495%   $32.3339   $32.33   $32.35   $32.30  
  Purchase #3 $89.32   13.782%   $101.6301   $101.63   $101.65   $101.60  
  Purchase #4 $45.74   11.243%   $50.8825   $50.88   $50.90   $50.90  
  Purchase #5 $167.64   7.749%   $180.6304   $180.63   $180.65   $180.60  
  Purchase #6 $35.85   7.168%   $38.4197   $38.42   $38.40   $38.40  
  Purchase #7 $230.45   7.246%   $247.1484   $247.15   $247.15   $247.10  
  7 purchase totals = $707.47       $765.6586   $765.65   $765.70   $765.50