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 $181.80   13.688%   $206.6848   $206.68   $206.70   $206.70  
  Purchase #2 $106.87   5.844%   $113.1155   $113.12   $113.10   $113.10  
  Purchase #3 $204.77   7.386%   $219.8943   $219.89   $219.90   $219.90  
  Purchase #4 $192.28   10.475%   $212.4213   $212.42   $212.40   $212.40  
  Purchase #5 $139.59   8.654%   $151.6701   $151.67   $151.65   $151.70  
  Purchase #6 $135.83   13.121%   $153.6523   $153.65   $153.65   $153.70  
  Purchase #7 $97.90   8.479%   $106.2009   $106.20   $106.20   $106.20  
  7 purchase totals = $1,059.04       $1,163.6392   $1,163.63   $1,163.60   $1,163.70