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 $196.26   6.460%   $208.9384   $208.94   $208.95   $208.90  
  Purchase #2 $209.35   5.669%   $221.2181   $221.22   $221.20   $221.20  
  Purchase #3 $15.43   10.261%   $17.0133   $17.01   $17.00   $17.00  
  Purchase #4 $195.61   12.812%   $220.6716   $220.67   $220.65   $220.70  
  Purchase #5 $134.52   3.721%   $139.5255   $139.53   $139.55   $139.50  
  Purchase #6 $130.90   4.506%   $136.7984   $136.80   $136.80   $136.80  
  Purchase #7 $109.97   8.747%   $119.5891   $119.59   $119.60   $119.60  
  7 purchase totals = $992.04       $1,063.7544   $1,063.76   $1,063.75   $1,063.70