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 $96.48   5.299%   $101.5925   $101.59   $101.60   $101.60  
  Purchase #2 $17.97   7.128%   $19.2509   $19.25   $19.25   $19.30  
  Purchase #3 $161.79   9.473%   $177.1164   $177.12   $177.10   $177.10  
  Purchase #4 $60.34   8.543%   $65.4948   $65.49   $65.50   $65.50  
  Purchase #5 $130.27   6.216%   $138.3676   $138.37   $138.35   $138.40  
  Purchase #6 $191.59   13.438%   $217.3359   $217.34   $217.35   $217.30  
  Purchase #7 $224.42   10.327%   $247.5959   $247.60   $247.60   $247.60  
  7 purchase totals = $882.86       $966.7540   $966.76   $966.75   $966.80