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 $95.48   5.824%   $101.0408   $101.04   $101.05   $101.00  
  Purchase #2 $77.32   7.352%   $83.0046   $83.00   $83.00   $83.00  
  Purchase #3 $163.67   10.219%   $180.3954   $180.40   $180.40   $180.40  
  Purchase #4 $239.38   9.431%   $261.9559   $261.96   $261.95   $262.00  
  Purchase #5 $95.67   11.228%   $106.4118   $106.41   $106.40   $106.40  
  Purchase #6 $186.67   6.645%   $199.0742   $199.07   $199.05   $199.10  
  Purchase #7 $237.97   10.291%   $262.4595   $262.46   $262.45   $262.50  
  7 purchase totals = $1,096.16       $1,194.3422   $1,194.34   $1,194.30   $1,194.40