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 $168.63   9.590%   $184.8016   $184.80   $184.80   $184.80  
  Purchase #2 $220.68   5.426%   $232.6541   $232.65   $232.65   $232.70  
  Purchase #3 $244.83   7.244%   $262.5655   $262.57   $262.55   $262.60  
  Purchase #4 $135.49   8.242%   $146.6571   $146.66   $146.65   $146.70  
  Purchase #5 $32.27   12.373%   $36.2628   $36.26   $36.25   $36.30  
  Purchase #6 $172.85   9.164%   $188.69   $188.69   $188.70   $188.70  
  Purchase #7 $75.56   9.292%   $82.581   $82.58   $82.60   $82.60  
  7 purchase totals = $1,050.31       $1,134.2121   $1,134.21   $1,134.20   $1,134.40