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 $183.30   11.856%   $205.032   $205.03   $205.05   $205.00  
  Purchase #2 $139.32   9.155%   $152.0747   $152.07   $152.05   $152.10  
  Purchase #3 $120.29   13.375%   $136.3788   $136.38   $136.40   $136.40  
  Purchase #4 $207.75   4.710%   $217.535   $217.54   $217.55   $217.50  
  Purchase #5 $79.53   5.299%   $83.7443   $83.74   $83.75   $83.70  
  Purchase #6 $250.88   13.153%   $283.8782   $283.88   $283.90   $283.90  
  Purchase #7 $113.97   10.362%   $125.7796   $125.78   $125.80   $125.80  
  7 purchase totals = $1,095.04       $1,204.4226   $1,204.42   $1,204.50   $1,204.40