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 $208.99   8.242%   $226.215   $226.22   $226.20   $226.20  
  Purchase #2 $52.38   5.302%   $55.1572   $55.16   $55.15   $55.20  
  Purchase #3 $214.89   11.782%   $240.2083   $240.21   $240.20   $240.20  
  Purchase #4 $155.93   11.390%   $173.6904   $173.69   $173.70   $173.70  
  Purchase #5 $240.50   5.649%   $254.0858   $254.09   $254.10   $254.10  
  Purchase #6 $56.49   8.547%   $61.3182   $61.32   $61.30   $61.30  
  Purchase #7 $23.46   10.183%   $25.8489   $25.85   $25.85   $25.80  
  7 purchase totals = $952.64       $1,036.5238   $1,036.54   $1,036.50   $1,036.50