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 $153.64   5.804%   $162.5573   $162.56   $162.55   $162.60  
  Purchase #2 $101.89   12.180%   $114.3002   $114.30   $114.30   $114.30  
  Purchase #3 $63.52   9.393%   $69.4864   $69.49   $69.50   $69.50  
  Purchase #4 $114.76   3.747%   $119.0601   $119.06   $119.05   $119.10  
  Purchase #5 $184.43   3.346%   $190.601   $190.60   $190.60   $190.60  
  Purchase #6 $32.49   9.644%   $35.6233   $35.62   $35.60   $35.60  
  Purchase #7 $213.32   5.447%   $224.9395   $224.94   $224.95   $224.90  
  7 purchase totals = $864.05       $916.5678   $916.57   $916.55   $916.60