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 $210.79   11.770%   $235.6   $235.60   $235.60   $235.60  
  Purchase #2 $30.69   10.109%   $33.7925   $33.79   $33.80   $33.80  
  Purchase #3 $76.76   9.785%   $84.271   $84.27   $84.25   $84.30  
  Purchase #4 $244.58   4.395%   $255.3293   $255.33   $255.35   $255.30  
  Purchase #5 $94.26   11.637%   $105.229   $105.23   $105.25   $105.20  
  Purchase #6 $13.63   8.216%   $14.7498   $14.75   $14.75   $14.70  
  Purchase #7 $107.57   6.210%   $114.2501   $114.25   $114.25   $114.30  
  7 purchase totals = $778.28       $843.2217   $843.22   $843.25   $843.20