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 $169.96   13.523%   $192.9437   $192.94   $192.95   $192.90  
  Purchase #2 $232.79   10.509%   $257.2539   $257.25   $257.25   $257.30  
  Purchase #3 $222.69   13.455%   $252.6529   $252.65   $252.65   $252.70  
  Purchase #4 $99.28   5.827%   $105.065   $105.07   $105.05   $105.10  
  Purchase #5 $89.85   12.570%   $101.1441   $101.14   $101.15   $101.10  
  Purchase #6 $64.56   4.850%   $67.6912   $67.69   $67.70   $67.70  
  Purchase #7 $54.55   7.196%   $58.4754   $58.48   $58.50   $58.50  
  7 purchase totals = $933.68       $1,035.2262   $1,035.22   $1,035.25   $1,035.30