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 $220.58   5.488%   $232.6854   $232.69   $232.70   $232.70  
  Purchase #2 $37.45   11.864%   $41.8931   $41.89   $41.90   $41.90  
  Purchase #3 $10.90   11.745%   $12.1802   $12.18   $12.20   $12.20  
  Purchase #4 $209.61   11.546%   $233.8116   $233.81   $233.80   $233.80  
  Purchase #5 $155.85   10.122%   $171.6251   $171.63   $171.65   $171.60  
  Purchase #6 $114.71   5.861%   $121.4332   $121.43   $121.45   $121.40  
  Purchase #7 $233.41   12.546%   $262.6936   $262.69   $262.70   $262.70  
  7 purchase totals = $982.51       $1,076.3222   $1,076.32   $1,076.40   $1,076.30