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 $62.29   5.543%   $65.7427   $65.74   $65.75   $65.70  
  Purchase #2 $239.74   11.309%   $266.8522   $266.85   $266.85   $266.90  
  Purchase #3 $78.54   8.168%   $84.9551   $84.96   $84.95   $85.00  
  Purchase #4 $205.53   13.698%   $233.6835   $233.68   $233.70   $233.70  
  Purchase #5 $140.46   8.491%   $152.3865   $152.39   $152.40   $152.40  
  Purchase #6 $32.84   12.623%   $36.9854   $36.99   $37.00   $37.00  
  Purchase #7 $62.42   6.519%   $66.4892   $66.49   $66.50   $66.50  
  7 purchase totals = $821.82       $907.0946   $907.10   $907.15   $907.20