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 $174.62   11.837%   $195.2898   $195.29   $195.30   $195.30  
  Purchase #2 $31.43   11.511%   $35.0479   $35.05   $35.05   $35.00  
  Purchase #3 $248.81   11.140%   $276.5274   $276.53   $276.55   $276.50  
  Purchase #4 $213.61   13.670%   $242.8105   $242.81   $242.80   $242.80  
  Purchase #5 $135.80   4.427%   $141.8119   $141.81   $141.80   $141.80  
  Purchase #6 $164.58   4.641%   $172.2182   $172.22   $172.20   $172.20  
  Purchase #7 $98.76   3.869%   $102.581   $102.58   $102.60   $102.60  
  7 purchase totals = $1,067.61       $1,166.2867   $1,166.29   $1,166.30   $1,166.20