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 $63.36   3.510%   $65.5839   $65.58   $65.60   $65.60  
  Purchase #2 $218.41   4.228%   $227.6444   $227.64   $227.65   $227.60  
  Purchase #3 $150.68   9.552%   $165.073   $165.07   $165.05   $165.10  
  Purchase #4 $203.61   8.496%   $220.9087   $220.91   $220.90   $220.90  
  Purchase #5 $95.71   6.279%   $101.7196   $101.72   $101.70   $101.70  
  Purchase #6 $53.91   7.788%   $58.1085   $58.11   $58.10   $58.10  
  Purchase #7 $231.28   6.247%   $245.7281   $245.73   $245.75   $245.70  
  7 purchase totals = $1,016.96       $1,084.7662   $1,084.76   $1,084.75   $1,084.70