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 $67.61   4.459%   $70.6247   $70.62   $70.60   $70.60  
  Purchase #2 $228.88   3.831%   $237.6484   $237.65   $237.65   $237.60  
  Purchase #3 $152.81   5.395%   $161.0541   $161.05   $161.05   $161.10  
  Purchase #4 $52.38   12.140%   $58.7389   $58.74   $58.75   $58.70  
  Purchase #5 $110.94   6.357%   $117.9925   $117.99   $118.00   $118.00  
  Purchase #6 $47.85   13.451%   $54.2863   $54.29   $54.30   $54.30  
  Purchase #7 $54.52   10.535%   $60.2637   $60.26   $60.25   $60.30  
  7 purchase totals = $714.99       $760.6086   $760.60   $760.60   $760.60