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 $216.48   11.723%   $241.858   $241.86   $241.85   $241.90  
  Purchase #2 $144.37   8.855%   $157.154   $157.15   $157.15   $157.20  
  Purchase #3 $11.69   3.775%   $12.1313   $12.13   $12.15   $12.10  
  Purchase #4 $145.94   8.165%   $157.856   $157.86   $157.85   $157.90  
  Purchase #5 $246.75   3.160%   $254.5473   $254.55   $254.55   $254.50  
  Purchase #6 $61.73   4.834%   $64.714   $64.71   $64.70   $64.70  
  Purchase #7 $130.83   10.418%   $144.4599   $144.46   $144.45   $144.50  
  7 purchase totals = $957.79       $1,032.7205   $1,032.72   $1,032.70   $1,032.80