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 $183.28   7.454%   $196.9417   $196.94   $196.95   $196.90  
  Purchase #2 $227.74   11.559%   $254.0645   $254.06   $254.05   $254.10  
  Purchase #3 $230.83   11.865%   $258.218   $258.22   $258.20   $258.20  
  Purchase #4 $121.41   4.170%   $126.4728   $126.47   $126.45   $126.50  
  Purchase #5 $144.94   8.475%   $157.2237   $157.22   $157.20   $157.20  
  Purchase #6 $66.79   9.545%   $73.1651   $73.17   $73.15   $73.20  
  Purchase #7 $159.71   7.430%   $171.5765   $171.58   $171.60   $171.60  
  7 purchase totals = $1,134.70       $1,237.6623   $1,237.66   $1,237.60   $1,237.70