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 $59.39   3.266%   $61.3297   $61.33   $61.35   $61.30  
  Purchase #2 $188.40   13.463%   $213.7643   $213.76   $213.75   $213.80  
  Purchase #3 $235.36   11.312%   $261.9839   $261.98   $262.00   $262.00  
  Purchase #4 $104.97   7.440%   $112.7798   $112.78   $112.80   $112.80  
  Purchase #5 $169.94   10.520%   $187.8177   $187.82   $187.80   $187.80  
  Purchase #6 $189.40   12.452%   $212.9841   $212.98   $213.00   $213.00  
  Purchase #7 $201.81   5.508%   $212.9257   $212.93   $212.95   $212.90  
  7 purchase totals = $1,149.27       $1,263.5852   $1,263.58   $1,263.65   $1,263.60