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 $83.33   13.722%   $94.7645   $94.76   $94.75   $94.80  
  Purchase #2 $233.89   3.788%   $242.7498   $242.75   $242.75   $242.70  
  Purchase #3 $159.78   9.369%   $174.7498   $174.75   $174.75   $174.70  
  Purchase #4 $49.95   8.468%   $54.1798   $54.18   $54.20   $54.20  
  Purchase #5 $109.85   11.743%   $122.7497   $122.75   $122.75   $122.70  
  Purchase #6 $190.77   8.543%   $207.0675   $207.07   $207.05   $207.10  
  Purchase #7 $33.81   4.106%   $35.1982   $35.20   $35.20   $35.20  
  7 purchase totals = $861.38       $931.4593   $931.46   $931.45   $931.40