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 $95.28   7.418%   $102.3479   $102.35   $102.35   $102.30  
  Purchase #2 $104.47   6.433%   $111.1906   $111.19   $111.20   $111.20  
  Purchase #3 $43.81   9.309%   $47.8883   $47.89   $47.90   $47.90  
  Purchase #4 $160.51   11.472%   $178.9237   $178.92   $178.90   $178.90  
  Purchase #5 $194.55   4.735%   $203.7619   $203.76   $203.75   $203.80  
  Purchase #6 $73.64   5.184%   $77.4575   $77.46   $77.45   $77.50  
  Purchase #7 $224.66   8.606%   $243.9942   $243.99   $244.00   $244.00  
  7 purchase totals = $896.92       $965.5641   $965.56   $965.55   $965.60