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 $212.69   11.773%   $237.73   $237.73   $237.75   $237.70  
  Purchase #2 $137.59   12.287%   $154.4957   $154.50   $154.50   $154.50  
  Purchase #3 $123.65   11.542%   $137.9217   $137.92   $137.90   $137.90  
  Purchase #4 $196.70   4.866%   $206.2714   $206.27   $206.25   $206.30  
  Purchase #5 $211.75   12.792%   $238.8371   $238.84   $238.85   $238.80  
  Purchase #6 $225.94   8.543%   $245.2421   $245.24   $245.25   $245.20  
  Purchase #7 $126.89   7.297%   $136.1492   $136.15   $136.15   $136.10  
  7 purchase totals = $1,235.21       $1,356.6472   $1,356.65   $1,356.65   $1,356.50