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 $60.92   11.763%   $68.086   $68.09   $68.10   $68.10  
  Purchase #2 $191.99   3.698%   $199.0898   $199.09   $199.10   $199.10  
  Purchase #3 $69.43   6.468%   $73.9207   $73.92   $73.90   $73.90  
  Purchase #4 $234.81   13.622%   $266.7958   $266.80   $266.80   $266.80  
  Purchase #5 $45.44   6.245%   $48.2777   $48.28   $48.30   $48.30  
  Purchase #6 $68.34   8.597%   $74.2152   $74.22   $74.20   $74.20  
  Purchase #7 $192.86   11.604%   $215.2395   $215.24   $215.25   $215.20  
  7 purchase totals = $863.79       $945.6247   $945.64   $945.65   $945.60