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 $64.53   11.241%   $71.7838   $71.78   $71.80   $71.80  
  Purchase #2 $192.83   8.136%   $208.5186   $208.52   $208.50   $208.50  
  Purchase #3 $195.79   3.488%   $202.6192   $202.62   $202.60   $202.60  
  Purchase #4 $165.60   10.115%   $182.3504   $182.35   $182.35   $182.40  
  Purchase #5 $56.75   3.111%   $58.5155   $58.52   $58.50   $58.50  
  Purchase #6 $10.64   13.582%   $12.0851   $12.09   $12.10   $12.10  
  Purchase #7 $186.56   13.304%   $211.3799   $211.38   $211.40   $211.40  
  7 purchase totals = $872.70       $947.2525   $947.26   $947.25   $947.30