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 $208.31   12.805%   $234.9841   $234.98   $235.00   $235.00  
  Purchase #2 $131.37   4.397%   $137.1463   $137.15   $137.15   $137.10  
  Purchase #3 $114.83   7.752%   $123.7316   $123.73   $123.75   $123.70  
  Purchase #4 $233.49   8.431%   $253.1755   $253.18   $253.20   $253.20  
  Purchase #5 $147.99   6.538%   $157.6656   $157.67   $157.65   $157.70  
  Purchase #6 $95.53   3.818%   $99.1773   $99.18   $99.20   $99.20  
  Purchase #7 $132.79   13.783%   $151.0924   $151.09   $151.10   $151.10  
  7 purchase totals = $1,064.31       $1,156.9728   $1,156.98   $1,157.05   $1,157.00