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 $54.69   5.422%   $57.6553   $57.66   $57.65   $57.70  
  Purchase #2 $110.48   4.448%   $115.3942   $115.39   $115.40   $115.40  
  Purchase #3 $200.88   5.828%   $212.5873   $212.59   $212.60   $212.60  
  Purchase #4 $168.92   10.347%   $186.3982   $186.40   $186.40   $186.40  
  Purchase #5 $5.61   10.559%   $6.2024   $6.20   $6.20   $6.20  
  Purchase #6 $186.71   10.361%   $206.055   $206.06   $206.05   $206.10  
  Purchase #7 $217.65   8.122%   $235.3275   $235.33   $235.35   $235.30  
  7 purchase totals = $944.94       $1,019.6199   $1,019.63   $1,019.65   $1,019.70