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 $35.32   5.519%   $37.2693   $37.27   $37.25   $37.30  
  Purchase #2 $108.71   3.581%   $112.6029   $112.60   $112.60   $112.60  
  Purchase #3 $127.97   8.581%   $138.9511   $138.95   $138.95   $139.00  
  Purchase #4 $156.29   4.128%   $162.7417   $162.74   $162.75   $162.70  
  Purchase #5 $153.63   13.300%   $174.0628   $174.06   $174.05   $174.10  
  Purchase #6 $33.74   4.312%   $35.1949   $35.19   $35.20   $35.20  
  Purchase #7 $70.42   3.163%   $72.6474   $72.65   $72.65   $72.60  
  7 purchase totals = $686.08       $733.4701   $733.46   $733.45   $733.50