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 $146.41   7.655%   $157.6177   $157.62   $157.60   $157.60  
  Purchase #2 $197.80   3.236%   $204.2008   $204.20   $204.20   $204.20  
  Purchase #3 $211.34   6.468%   $225.0095   $225.01   $225.00   $225.00  
  Purchase #4 $73.76   3.837%   $76.5902   $76.59   $76.60   $76.60  
  Purchase #5 $76.89   12.169%   $86.2467   $86.25   $86.25   $86.20  
  Purchase #6 $238.85   13.835%   $271.8949   $271.89   $271.90   $271.90  
  Purchase #7 $19.76   12.694%   $22.2683   $22.27   $22.25   $22.30  
  7 purchase totals = $964.81       $1,043.8281   $1,043.83   $1,043.80   $1,043.80