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 $44.64   5.615%   $47.1465   $47.15   $47.15   $47.10  
  Purchase #2 $104.66   6.763%   $111.7382   $111.74   $111.75   $111.70  
  Purchase #3 $29.84   9.688%   $32.7309   $32.73   $32.75   $32.70  
  Purchase #4 $159.96   5.631%   $168.9673   $168.97   $168.95   $169.00  
  Purchase #5 $215.96   11.334%   $240.4369   $240.44   $240.45   $240.40  
  Purchase #6 $177.59   11.680%   $198.3325   $198.33   $198.35   $198.30  
  Purchase #7 $123.67   10.277%   $136.3796   $136.38   $136.40   $136.40  
  7 purchase totals = $856.32       $935.7319   $935.74   $935.80   $935.60