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 $174.37   12.721%   $196.5516   $196.55   $196.55   $196.60  
  Purchase #2 $102.66   11.460%   $114.4248   $114.42   $114.40   $114.40  
  Purchase #3 $55.44   5.663%   $58.5796   $58.58   $58.60   $58.60  
  Purchase #4 $112.38   10.590%   $124.281   $124.28   $124.30   $124.30  
  Purchase #5 $227.97   10.827%   $252.6523   $252.65   $252.65   $252.70  
  Purchase #6 $129.28   10.420%   $142.751   $142.75   $142.75   $142.80  
  Purchase #7 $214.94   5.263%   $226.2523   $226.25   $226.25   $226.30  
  7 purchase totals = $1,017.04       $1,115.4926   $1,115.48   $1,115.50   $1,115.70