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 $62.66   10.763%   $69.4041   $69.40   $69.40   $69.40  
  Purchase #2 $115.37   7.602%   $124.1404   $124.14   $124.15   $124.10  
  Purchase #3 $50.82   13.391%   $57.6253   $57.63   $57.65   $57.60  
  Purchase #4 $190.96   11.406%   $212.7409   $212.74   $212.75   $212.70  
  Purchase #5 $214.81   6.777%   $229.3677   $229.37   $229.35   $229.40  
  Purchase #6 $223.32   8.397%   $242.0722   $242.07   $242.05   $242.10  
  Purchase #7 $100.34   10.831%   $111.2078   $111.21   $111.20   $111.20  
  7 purchase totals = $958.28       $1,046.5584   $1,046.56   $1,046.55   $1,046.50