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 $164.97   7.127%   $176.7274   $176.73   $176.75   $176.70  
  Purchase #2 $196.51   13.342%   $222.7284   $222.73   $222.75   $222.70  
  Purchase #3 $35.41   8.697%   $38.4896   $38.49   $38.50   $38.50  
  Purchase #4 $208.94   11.485%   $232.9368   $232.94   $232.95   $232.90  
  Purchase #5 $155.59   8.624%   $169.0081   $169.01   $169.00   $169.00  
  Purchase #6 $33.89   4.647%   $35.4649   $35.46   $35.45   $35.50  
  Purchase #7 $213.38   3.260%   $220.3362   $220.34   $220.35   $220.30  
  7 purchase totals = $1,008.69       $1,095.6914   $1,095.70   $1,095.75   $1,095.60