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 $233.64   8.730%   $254.0368   $254.04   $254.05   $254.00  
  Purchase #2 $108.33   5.519%   $114.3087   $114.31   $114.30   $114.30  
  Purchase #3 $213.38   5.758%   $225.6664   $225.67   $225.65   $225.70  
  Purchase #4 $57.92   8.109%   $62.6167   $62.62   $62.60   $62.60  
  Purchase #5 $169.91   3.353%   $175.6071   $175.61   $175.60   $175.60  
  Purchase #6 $46.77   9.135%   $51.0424   $51.04   $51.05   $51.00  
  Purchase #7 $203.76   11.777%   $227.7568   $227.76   $227.75   $227.80  
  7 purchase totals = $1,033.71       $1,111.0349   $1,111.05   $1,111.00   $1,111.00