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 $197.42   5.181%   $207.6483   $207.65   $207.65   $207.60  
  Purchase #2 $52.46   11.600%   $58.5454   $58.55   $58.55   $58.50  
  Purchase #3 $41.73   13.821%   $47.4975   $47.50   $47.50   $47.50  
  Purchase #4 $176.35   13.797%   $200.681   $200.68   $200.70   $200.70  
  Purchase #5 $185.60   8.313%   $201.0289   $201.03   $201.05   $201.00  
  Purchase #6 $18.93   4.458%   $19.7739   $19.77   $19.75   $19.80  
  Purchase #7 $206.58   4.704%   $216.2975   $216.30   $216.30   $216.30  
  7 purchase totals = $879.07       $951.4725   $951.48   $951.50   $951.40