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 $60.49   5.117%   $63.5853   $63.59   $63.60   $63.60  
  Purchase #2 $183.26   3.864%   $190.3412   $190.34   $190.35   $190.30  
  Purchase #3 $187.34   12.873%   $211.4563   $211.46   $211.45   $211.50  
  Purchase #4 $185.53   6.746%   $198.0459   $198.05   $198.05   $198.00  
  Purchase #5 $111.46   10.838%   $123.54   $123.54   $123.55   $123.50  
  Purchase #6 $177.85   9.747%   $195.185   $195.19   $195.20   $195.20  
  Purchase #7 $215.53   5.162%   $226.6557   $226.66   $226.65   $226.70  
  7 purchase totals = $1,121.46       $1,208.8094   $1,208.83   $1,208.85   $1,208.80