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 $62.50   8.775%   $67.9844   $67.98   $68.00   $68.00  
  Purchase #2 $158.59   3.526%   $164.1819   $164.18   $164.20   $164.20  
  Purchase #3 $14.88   8.603%   $16.1601   $16.16   $16.15   $16.20  
  Purchase #4 $57.79   7.138%   $61.9151   $61.92   $61.90   $61.90  
  Purchase #5 $186.33   6.685%   $198.7862   $198.79   $198.80   $198.80  
  Purchase #6 $128.45   12.833%   $144.934   $144.93   $144.95   $144.90  
  Purchase #7 $244.74   8.694%   $266.0177   $266.02   $266.00   $266.00  
  7 purchase totals = $853.28       $919.9794   $919.98   $920.00   $920.00