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 $86.81   8.794%   $94.4441   $94.44   $94.45   $94.40  
  Purchase #2 $188.50   4.691%   $197.3425   $197.34   $197.35   $197.30  
  Purchase #3 $83.84   3.470%   $86.7492   $86.75   $86.75   $86.70  
  Purchase #4 $219.52   7.547%   $236.0872   $236.09   $236.10   $236.10  
  Purchase #5 $158.64   3.219%   $163.7466   $163.75   $163.75   $163.70  
  Purchase #6 $217.32   9.730%   $238.4652   $238.47   $238.45   $238.50  
  Purchase #7 $168.47   13.727%   $191.5959   $191.60   $191.60   $191.60  
  7 purchase totals = $1,123.10       $1,208.4307   $1,208.44   $1,208.45   $1,208.30