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 $75.93   8.145%   $82.1145   $82.11   $82.10   $82.10  
  Purchase #2 $245.42   3.752%   $254.6282   $254.63   $254.65   $254.60  
  Purchase #3 $54.47   3.691%   $56.4805   $56.48   $56.50   $56.50  
  Purchase #4 $199.70   6.863%   $213.4054   $213.41   $213.40   $213.40  
  Purchase #5 $223.59   3.398%   $231.1876   $231.19   $231.20   $231.20  
  Purchase #6 $137.61   9.426%   $150.5811   $150.58   $150.60   $150.60  
  Purchase #7 $23.39   9.635%   $25.6436   $25.64   $25.65   $25.60  
  7 purchase totals = $960.11       $1,014.0409   $1,014.04   $1,014.10   $1,014.00