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 $63.71   5.262%   $67.0624   $67.06   $67.05   $67.10  
  Purchase #2 $5.41   12.476%   $6.085   $6.09   $6.10   $6.10  
  Purchase #3 $23.58   13.552%   $26.7756   $26.78   $26.80   $26.80  
  Purchase #4 $152.49   6.658%   $162.6428   $162.64   $162.65   $162.60  
  Purchase #5 $45.30   3.791%   $47.0173   $47.02   $47.00   $47.00  
  Purchase #6 $54.63   5.132%   $57.4336   $57.43   $57.45   $57.40  
  Purchase #7 $82.87   11.267%   $92.207   $92.21   $92.20   $92.20  
  7 purchase totals = $427.99       $459.2237   $459.23   $459.25   $459.20