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 $203.82   5.315%   $214.653   $214.65   $214.65   $214.70  
  Purchase #2 $195.44   6.776%   $208.683   $208.68   $208.70   $208.70  
  Purchase #3 $94.47   4.614%   $98.8288   $98.83   $98.85   $98.80  
  Purchase #4 $135.33   12.676%   $152.4844   $152.48   $152.50   $152.50  
  Purchase #5 $46.91   11.742%   $52.4182   $52.42   $52.40   $52.40  
  Purchase #6 $197.60   5.650%   $208.7644   $208.76   $208.75   $208.80  
  Purchase #7 $117.27   12.255%   $131.6414   $131.64   $131.65   $131.60  
  7 purchase totals = $990.84       $1,067.4732   $1,067.46   $1,067.50   $1,067.50