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 $211.70   7.569%   $227.7236   $227.72   $227.70   $227.70  
  Purchase #2 $114.66   9.353%   $125.3841   $125.38   $125.40   $125.40  
  Purchase #3 $132.76   6.339%   $141.1757   $141.18   $141.20   $141.20  
  Purchase #4 $201.32   8.755%   $218.9456   $218.95   $218.95   $218.90  
  Purchase #5 $209.30   13.444%   $237.4383   $237.44   $237.45   $237.40  
  Purchase #6 $73.93   11.190%   $82.2028   $82.20   $82.20   $82.20  
  Purchase #7 $186.73   12.784%   $210.6016   $210.60   $210.60   $210.60  
  7 purchase totals = $1,130.40       $1,243.4717   $1,243.47   $1,243.50   $1,243.40