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 $84.49   12.106%   $94.7184   $94.72   $94.70   $94.70  
  Purchase #2 $182.59   9.180%   $199.3518   $199.35   $199.35   $199.40  
  Purchase #3 $199.88   11.785%   $223.4359   $223.44   $223.45   $223.40  
  Purchase #4 $133.49   4.574%   $139.5958   $139.60   $139.60   $139.60  
  Purchase #5 $216.34   3.726%   $224.4008   $224.40   $224.40   $224.40  
  Purchase #6 $242.42   5.554%   $255.884   $255.88   $255.90   $255.90  
  Purchase #7 $44.61   5.290%   $46.9699   $46.97   $46.95   $47.00  
  7 purchase totals = $1,103.82       $1,184.3566   $1,184.36   $1,184.35   $1,184.40