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 $215.26   5.858%   $227.8699   $227.87   $227.85   $227.90  
  Purchase #2 $183.32   11.202%   $203.8555   $203.86   $203.85   $203.90  
  Purchase #3 $208.53   6.249%   $221.561   $221.56   $221.55   $221.60  
  Purchase #4 $193.50   7.255%   $207.5384   $207.54   $207.55   $207.50  
  Purchase #5 $218.63   4.619%   $228.7285   $228.73   $228.75   $228.70  
  Purchase #6 $65.61   10.165%   $72.2793   $72.28   $72.30   $72.30  
  Purchase #7 $43.62   6.274%   $46.3567   $46.36   $46.35   $46.40  
  7 purchase totals = $1,128.47       $1,208.1893   $1,208.20   $1,208.20   $1,208.30