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 $214.94   7.458%   $230.9702   $230.97   $230.95   $231.00  
  Purchase #2 $242.96   11.872%   $271.8042   $271.80   $271.80   $271.80  
  Purchase #3 $65.84   13.329%   $74.6158   $74.62   $74.60   $74.60  
  Purchase #4 $85.67   10.318%   $94.5094   $94.51   $94.50   $94.50  
  Purchase #5 $57.79   12.460%   $64.9906   $64.99   $65.00   $65.00  
  Purchase #6 $13.84   3.730%   $14.3562   $14.36   $14.35   $14.40  
  Purchase #7 $44.44   8.874%   $48.3836   $48.38   $48.40   $48.40  
  7 purchase totals = $725.48       $799.6300   $799.63   $799.60   $799.70