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 $208.74   11.273%   $232.2713   $232.27   $232.25   $232.30  
  Purchase #2 $203.68   4.271%   $212.3792   $212.38   $212.40   $212.40  
  Purchase #3 $222.43   7.793%   $239.764   $239.76   $239.75   $239.80  
  Purchase #4 $154.86   5.177%   $162.8771   $162.88   $162.90   $162.90  
  Purchase #5 $49.42   5.123%   $51.9518   $51.95   $51.95   $52.00  
  Purchase #6 $69.98   4.372%   $73.0395   $73.04   $73.05   $73.00  
  Purchase #7 $208.77   10.679%   $231.0645   $231.06   $231.05   $231.10  
  7 purchase totals = $1,117.88       $1,203.3474   $1,203.34   $1,203.35   $1,203.50