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 $163.46   11.373%   $182.0503   $182.05   $182.05   $182.10  
  Purchase #2 $103.65   6.436%   $110.3209   $110.32   $110.30   $110.30  
  Purchase #3 $19.60   5.557%   $20.6892   $20.69   $20.70   $20.70  
  Purchase #4 $216.68   7.732%   $233.4337   $233.43   $233.45   $233.40  
  Purchase #5 $208.81   4.786%   $218.8036   $218.80   $218.80   $218.80  
  Purchase #6 $25.78   10.163%   $28.4   $28.40   $28.40   $28.40  
  Purchase #7 $48.71   3.731%   $50.5274   $50.53   $50.55   $50.50  
  7 purchase totals = $786.69       $844.2251   $844.22   $844.25   $844.20