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 $93.63   4.727%   $98.0559   $98.06   $98.05   $98.10  
  Purchase #2 $208.83   6.451%   $222.3016   $222.30   $222.30   $222.30  
  Purchase #3 $157.26   9.855%   $172.758   $172.76   $172.75   $172.80  
  Purchase #4 $22.46   6.392%   $23.8956   $23.90   $23.90   $23.90  
  Purchase #5 $119.71   11.456%   $133.424   $133.42   $133.40   $133.40  
  Purchase #6 $47.78   3.754%   $49.5737   $49.57   $49.55   $49.60  
  Purchase #7 $210.46   7.843%   $226.9664   $226.97   $226.95   $227.00  
  7 purchase totals = $860.13       $926.9752   $926.98   $926.90   $927.10