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 $101.25   4.452%   $105.7577   $105.76   $105.75   $105.80  
  Purchase #2 $194.85   6.167%   $206.8664   $206.87   $206.85   $206.90  
  Purchase #3 $73.51   13.757%   $83.6228   $83.62   $83.60   $83.60  
  Purchase #4 $44.43   4.228%   $46.3085   $46.31   $46.30   $46.30  
  Purchase #5 $114.99   8.656%   $124.9435   $124.94   $124.95   $124.90  
  Purchase #6 $234.46   8.546%   $254.497   $254.50   $254.50   $254.50  
  Purchase #7 $185.50   10.544%   $205.0591   $205.06   $205.05   $205.10  
  7 purchase totals = $948.99       $1,027.0550   $1,027.06   $1,027.00   $1,027.10