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 $59.85   9.610%   $65.6016   $65.60   $65.60   $65.60  
  Purchase #2 $249.76   6.353%   $265.6273   $265.63   $265.65   $265.60  
  Purchase #3 $216.94   12.195%   $243.3958   $243.40   $243.40   $243.40  
  Purchase #4 $96.81   9.638%   $106.1405   $106.14   $106.15   $106.10  
  Purchase #5 $32.60   6.572%   $34.7425   $34.74   $34.75   $34.70  
  Purchase #6 $138.25   10.407%   $152.6377   $152.64   $152.65   $152.60  
  Purchase #7 $217.33   11.365%   $242.0296   $242.03   $242.05   $242.00  
  7 purchase totals = $1,011.54       $1,110.1750   $1,110.18   $1,110.25   $1,110.00