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 $200.58   10.691%   $222.024   $222.02   $222.00   $222.00  
  Purchase #2 $26.84   13.418%   $30.4414   $30.44   $30.45   $30.40  
  Purchase #3 $159.55   3.185%   $164.6317   $164.63   $164.65   $164.60  
  Purchase #4 $182.63   3.551%   $189.1152   $189.12   $189.10   $189.10  
  Purchase #5 $133.86   10.233%   $147.5579   $147.56   $147.55   $147.60  
  Purchase #6 $226.36   4.692%   $236.9808   $236.98   $237.00   $237.00  
  Purchase #7 $164.86   3.347%   $170.3779   $170.38   $170.40   $170.40  
  7 purchase totals = $1,094.68       $1,161.1289   $1,161.13   $1,161.15   $1,161.10