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 $243.58   7.574%   $262.0287   $262.03   $262.05   $262.00  
  Purchase #2 $53.61   9.499%   $58.7024   $58.70   $58.70   $58.70  
  Purchase #3 $82.87   6.323%   $88.1099   $88.11   $88.10   $88.10  
  Purchase #4 $121.66   9.528%   $133.2518   $133.25   $133.25   $133.30  
  Purchase #5 $183.66   4.574%   $192.0606   $192.06   $192.05   $192.10  
  Purchase #6 $222.93   6.119%   $236.5711   $236.57   $236.55   $236.60  
  Purchase #7 $237.87   7.518%   $255.7531   $255.75   $255.75   $255.80  
  7 purchase totals = $1,146.18       $1,226.4776   $1,226.47   $1,226.45   $1,226.60