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 $208.59   10.599%   $230.6985   $230.70   $230.70   $230.70  
  Purchase #2 $190.90   10.334%   $210.6276   $210.63   $210.65   $210.60  
  Purchase #3 $212.42   11.449%   $236.74   $236.74   $236.75   $236.70  
  Purchase #4 $140.54   3.461%   $145.4041   $145.40   $145.40   $145.40  
  Purchase #5 $186.82   6.724%   $199.3818   $199.38   $199.40   $199.40  
  Purchase #6 $101.95   11.488%   $113.662   $113.66   $113.65   $113.70  
  Purchase #7 $7.58   13.831%   $8.6284   $8.63   $8.65   $8.60  
  7 purchase totals = $1,048.80       $1,145.1424   $1,145.14   $1,145.20   $1,145.10