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 $224.34   7.661%   $241.5267   $241.53   $241.55   $241.50  
  Purchase #2 $32.57   8.533%   $35.3492   $35.35   $35.35   $35.30  
  Purchase #3 $158.55   8.493%   $172.0157   $172.02   $172.00   $172.00  
  Purchase #4 $168.35   11.216%   $187.2321   $187.23   $187.25   $187.20  
  Purchase #5 $97.95   5.626%   $103.4607   $103.46   $103.45   $103.50  
  Purchase #6 $229.60   13.438%   $260.4536   $260.45   $260.45   $260.50  
  Purchase #7 $221.55   10.756%   $245.3799   $245.38   $245.40   $245.40  
  7 purchase totals = $1,132.91       $1,245.4179   $1,245.42   $1,245.45   $1,245.40