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 $176.41   9.721%   $193.5588   $193.56   $193.55   $193.60  
  Purchase #2 $184.38   6.150%   $195.7194   $195.72   $195.70   $195.70  
  Purchase #3 $183.36   10.163%   $201.9949   $201.99   $202.00   $202.00  
  Purchase #4 $61.93   3.149%   $63.8802   $63.88   $63.90   $63.90  
  Purchase #5 $186.43   9.574%   $204.2788   $204.28   $204.30   $204.30  
  Purchase #6 $175.51   9.764%   $192.6468   $192.65   $192.65   $192.60  
  Purchase #7 $104.80   10.259%   $115.5514   $115.55   $115.55   $115.60  
  7 purchase totals = $1,072.82       $1,167.6303   $1,167.63   $1,167.65   $1,167.70