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 $191.53   5.148%   $201.39   $201.39   $201.40   $201.40  
  Purchase #2 $9.77   9.539%   $10.702   $10.70   $10.70   $10.70  
  Purchase #3 $237.87   12.706%   $268.0938   $268.09   $268.10   $268.10  
  Purchase #4 $115.56   3.172%   $119.2256   $119.23   $119.25   $119.20  
  Purchase #5 $27.81   4.574%   $29.082   $29.08   $29.10   $29.10  
  Purchase #6 $92.65   6.609%   $98.7732   $98.77   $98.75   $98.80  
  Purchase #7 $34.68   3.147%   $35.7714   $35.77   $35.75   $35.80  
  7 purchase totals = $709.87       $763.0380   $763.03   $763.05   $763.10