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 $65.95   5.502%   $69.5786   $69.58   $69.60   $69.60  
  Purchase #2 $228.78   4.404%   $238.8555   $238.86   $238.85   $238.90  
  Purchase #3 $134.73   7.555%   $144.9089   $144.91   $144.90   $144.90  
  Purchase #4 $40.97   8.766%   $44.5614   $44.56   $44.55   $44.60  
  Purchase #5 $246.47   5.660%   $260.4202   $260.42   $260.40   $260.40  
  Purchase #6 $188.36   5.744%   $199.1794   $199.18   $199.20   $199.20  
  Purchase #7 $190.47   12.150%   $213.6121   $213.61   $213.60   $213.60  
  7 purchase totals = $1,095.73       $1,171.1161   $1,171.12   $1,171.10   $1,171.20