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 $58.59   7.116%   $62.7593   $62.76   $62.75   $62.80  
  Purchase #2 $223.62   6.312%   $237.7349   $237.73   $237.75   $237.70  
  Purchase #3 $163.84   12.243%   $183.8989   $183.90   $183.90   $183.90  
  Purchase #4 $97.61   6.226%   $103.6872   $103.69   $103.70   $103.70  
  Purchase #5 $208.25   6.774%   $222.3569   $222.36   $222.35   $222.40  
  Purchase #6 $98.36   10.151%   $108.3445   $108.34   $108.35   $108.30  
  Purchase #7 $39.55   4.400%   $41.2902   $41.29   $41.30   $41.30  
  7 purchase totals = $889.82       $960.0719   $960.07   $960.10   $960.10