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 $219.76   7.509%   $236.2618   $236.26   $236.25   $236.30  
  Purchase #2 $214.34   10.243%   $236.2948   $236.29   $236.30   $236.30  
  Purchase #3 $12.48   13.496%   $14.1643   $14.16   $14.15   $14.20  
  Purchase #4 $92.47   6.307%   $98.3021   $98.30   $98.30   $98.30  
  Purchase #5 $40.54   5.119%   $42.6152   $42.62   $42.60   $42.60  
  Purchase #6 $244.27   11.127%   $271.4499   $271.45   $271.45   $271.40  
  Purchase #7 $88.28   9.555%   $96.7152   $96.72   $96.70   $96.70  
  7 purchase totals = $912.14       $995.8033   $995.80   $995.75   $995.80