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 $91.96   7.231%   $98.6096   $98.61   $98.60   $98.60  
  Purchase #2 $198.96   5.468%   $209.8391   $209.84   $209.85   $209.80  
  Purchase #3 $223.68   8.510%   $242.7152   $242.72   $242.70   $242.70  
  Purchase #4 $82.72   13.705%   $94.0568   $94.06   $94.05   $94.10  
  Purchase #5 $43.79   11.660%   $48.8959   $48.90   $48.90   $48.90  
  Purchase #6 $143.42   12.749%   $161.7046   $161.70   $161.70   $161.70  
  Purchase #7 $144.71   9.604%   $158.6079   $158.61   $158.60   $158.60  
  7 purchase totals = $929.24       $1,014.4291   $1,014.44   $1,014.40   $1,014.40