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 $146.64   4.219%   $152.8267   $152.83   $152.85   $152.80  
  Purchase #2 $235.78   11.274%   $262.3618   $262.36   $262.35   $262.40  
  Purchase #3 $15.72   12.255%   $17.6465   $17.65   $17.65   $17.60  
  Purchase #4 $162.27   9.347%   $177.4374   $177.44   $177.45   $177.40  
  Purchase #5 $119.75   4.334%   $124.94   $124.94   $124.95   $124.90  
  Purchase #6 $124.44   7.259%   $133.4731   $133.47   $133.45   $133.50  
  Purchase #7 $216.37   11.384%   $241.0016   $241.00   $241.00   $241.00  
  7 purchase totals = $1,020.97       $1,109.6871   $1,109.69   $1,109.70   $1,109.60