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 $146.73   4.495%   $153.3255   $153.33   $153.35   $153.30  
  Purchase #2 $71.98   6.323%   $76.5313   $76.53   $76.55   $76.50  
  Purchase #3 $16.70   11.240%   $18.5771   $18.58   $18.60   $18.60  
  Purchase #4 $40.87   5.341%   $43.0529   $43.05   $43.05   $43.10  
  Purchase #5 $212.97   8.772%   $231.6517   $231.65   $231.65   $231.70  
  Purchase #6 $77.74   4.534%   $81.2647   $81.26   $81.25   $81.30  
  Purchase #7 $115.74   4.719%   $121.2018   $121.20   $121.20   $121.20  
  7 purchase totals = $682.73       $725.6050   $725.60   $725.65   $725.70