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 $224.82   3.723%   $233.19   $233.19   $233.20   $233.20  
  Purchase #2 $111.71   5.650%   $118.0216   $118.02   $118.00   $118.00  
  Purchase #3 $55.36   12.826%   $62.4605   $62.46   $62.45   $62.50  
  Purchase #4 $226.74   6.278%   $240.9747   $240.97   $240.95   $241.00  
  Purchase #5 $156.89   11.165%   $174.4068   $174.41   $174.40   $174.40  
  Purchase #6 $198.61   3.600%   $205.76   $205.76   $205.75   $205.80  
  Purchase #7 $74.95   8.186%   $81.0854   $81.09   $81.10   $81.10  
  7 purchase totals = $1,049.08       $1,115.8990   $1,115.90   $1,115.85   $1,116.00