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 $182.58   8.770%   $198.5923   $198.59   $198.60   $198.60  
  Purchase #2 $112.77   4.611%   $117.9698   $117.97   $117.95   $118.00  
  Purchase #3 $11.47   9.233%   $12.529   $12.53   $12.55   $12.50  
  Purchase #4 $127.26   8.119%   $137.5922   $137.59   $137.60   $137.60  
  Purchase #5 $199.34   5.525%   $210.3535   $210.35   $210.35   $210.40  
  Purchase #6 $217.64   3.203%   $224.611   $224.61   $224.60   $224.60  
  Purchase #7 $206.40   6.729%   $220.2887   $220.29   $220.30   $220.30  
  7 purchase totals = $1,057.46       $1,121.9365   $1,121.93   $1,121.95   $1,122.00