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 $94.32   5.525%   $99.5312   $99.53   $99.55   $99.50  
  Purchase #2 $230.94   10.354%   $254.8515   $254.85   $254.85   $254.90  
  Purchase #3 $95.49   10.234%   $105.2624   $105.26   $105.25   $105.30  
  Purchase #4 $145.60   8.226%   $157.5771   $157.58   $157.60   $157.60  
  Purchase #5 $66.69   13.748%   $75.8585   $75.86   $75.85   $75.90  
  Purchase #6 $49.55   8.297%   $53.6612   $53.66   $53.65   $53.70  
  Purchase #7 $250.58   6.757%   $267.5117   $267.51   $267.50   $267.50  
  7 purchase totals = $933.17       $1,014.2536   $1,014.25   $1,014.25   $1,014.40