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 $222.38   5.437%   $234.4708   $234.47   $234.45   $234.50  
  Purchase #2 $119.32   6.394%   $126.9493   $126.95   $126.95   $126.90  
  Purchase #3 $118.63   6.672%   $126.545   $126.55   $126.55   $126.50  
  Purchase #4 $137.26   3.302%   $141.7923   $141.79   $141.80   $141.80  
  Purchase #5 $130.82   10.259%   $144.2408   $144.24   $144.25   $144.20  
  Purchase #6 $161.68   13.464%   $183.4486   $183.45   $183.45   $183.40  
  Purchase #7 $58.83   11.280%   $65.466   $65.47   $65.45   $65.50  
  7 purchase totals = $948.92       $1,022.9128   $1,022.92   $1,022.90   $1,022.80