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 $183.92   5.588%   $194.1974   $194.20   $194.20   $194.20  
  Purchase #2 $223.81   4.836%   $234.6335   $234.63   $234.65   $234.60  
  Purchase #3 $12.60   4.534%   $13.1713   $13.17   $13.15   $13.20  
  Purchase #4 $161.63   11.650%   $180.4599   $180.46   $180.45   $180.50  
  Purchase #5 $105.74   8.358%   $114.5777   $114.58   $114.60   $114.60  
  Purchase #6 $47.47   9.344%   $51.9056   $51.91   $51.90   $51.90  
  Purchase #7 $216.99   5.141%   $228.1455   $228.15   $228.15   $228.10  
  7 purchase totals = $952.16       $1,017.0909   $1,017.10   $1,017.10   $1,017.10