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 $195.82   5.569%   $206.7252   $206.73   $206.75   $206.70  
  Purchase #2 $192.76   3.558%   $199.6184   $199.62   $199.60   $199.60  
  Purchase #3 $170.62   10.663%   $188.8132   $188.81   $188.80   $188.80  
  Purchase #4 $108.36   12.116%   $121.4889   $121.49   $121.50   $121.50  
  Purchase #5 $238.37   5.520%   $251.528   $251.53   $251.55   $251.50  
  Purchase #6 $25.68   3.228%   $26.509   $26.51   $26.50   $26.50  
  Purchase #7 $111.95   9.169%   $122.2147   $122.21   $122.20   $122.20  
  7 purchase totals = $1,043.56       $1,116.8974   $1,116.90   $1,116.90   $1,116.80